有用科技小编2026/10/23
浏览9778
阅读9分钟PDF加签名主要有三条路：手写签名适合个人快速签，电子签名是把姓名做成签名图贴上去，数字签名需要证书、能验证真伪。三种都要用支持PDF编辑的工具，动手前先确认文件没加密、不是纯扫描件。
多数人签不上，是文件权限被限制了，或者手里的本来就是图片型扫描件，文件本身没坏，不用重做一份。以下方法在 Windows 10/11 实测可用。
适用系统：Windows 10/11；最后更新：2026-10-23。
「加签名」其实分三种，先对号入座
点签字位置没反应，或者跳出来一句「此文档不允许签名」，这是最常见的两个卡点；数字签名走完流程还会碰到「签名无效」的提示。它们的原因完全不同，前者出在权限和安全设置上，后者多半是证书或者文档被改动过。
先分清自己要的是哪一种，再准备素材，比随便装个工具乱点省时间。手写签名是纸笔写好拍照贴进去，电子签名是输入姓名生成签名图，数字签名要 CA 机构签发的证书文件（.pfx/.p12）或 UKey；如果手里只有扫描件，得先做文字识别转成可编辑 PDF，否则签名只是浮在整页图上，看着别扭。
'/%3E%3Crect%20x='28'%20y='64'%20width='264'%20height='96'%20rx='12'%20fill='%23ffffff'%20stroke='%23dbe3ec'%20stroke-width='1.5'/%3E%3Crect%20x='28'%20y='64'%20width='264'%20height='6'%20rx='3'%20fill='%232b86f0'/%3E%3Ccircle%20cx='58'%20cy='106'%20r='17'%20fill='%23e1eefd'/%3E%3Cg%20transform='translate(58,106)'%3E%3Cpath%20d='M0%20-9%20L9%208%20L-9%208%20Z'%20fill='none'%20stroke='%232b86f0'%20stroke-width='2.4'%20stroke-linejoin='round'/%3E%3Cline%20x1='0'%20y1='-2'%20x2='0'%20y2='3'%20stroke='%232b86f0'%20stroke-width='2.4'%20stroke-linecap='round'/%3E%3Ccircle%20cx='0'%20cy='6'%20r='1.4'%20fill='%232b86f0'/%3E%3C/g%3E%3Ctext%20x='82.0'%20y='102'%20font-family='Segoe%20UI,Microsoft%20YaHei,PingFang%20SC,sans-serif'%20font-size='15'%20fill='%231f2d3d'%20text-anchor='start'%20font-weight='700'%3E手写签名%3C/text%3E%3Ctext%20x='82.0'%20y='124'%20font-family='Segoe%20UI,Microsoft%20YaHei,PingFang%20SC,sans-serif'%20font-size='12.5'%20fill='%235b6b7b'%20text-anchor='start'%20font-weight='400'%3E纸笔写好拍照再贴进去%3C/text%3E%3Crect%20x='308'%20y='64'%20width='264'%20height='96'%20rx='12'%20fill='%23ffffff'%20stroke='%23dbe3ec'%20stroke-width='1.5'/%3E%3Crect%20x='308'%20y='64'%20width='264'%20height='6'%20rx='3'%20fill='%23155fc4'/%3E%3Ccircle%20cx='338'%20cy='106'%20r='17'%20fill='%23e1eefd'/%3E%3Cg%20transform='translate(338,106)'%3E%3Cline%20x1='-7'%20y1='-7'%20x2='7'%20y2='7'%20stroke='%232b86f0'%20stroke-width='2.6'%20stroke-linecap='round'/%3E%3Cline%20x1='7'%20y1='-7'%20x2='-7'%20y2='7'%20stroke='%232b86f0'%20stroke-width='2.6'%20stroke-linecap='round'/%3E%3C/g%3E%3Ctext%20x='362.0'%20y='102'%20font-family='Segoe%20UI,Microsoft%20YaHei,PingFang%20SC,sans-serif'%20font-size='15'%20fill='%231f2d3d'%20text-anchor='start'%20font-weight='700'%3E电子签名%3C/text%3E%3Ctext%20x='362.0'%20y='124'%20font-family='Segoe%20UI,Microsoft%20YaHei,PingFang%20SC,sans-serif'%20font-size='12.5'%20fill='%235b6b7b'%20text-anchor='start'%20font-weight='400'%3E输入姓名生成签名图%3C/text%3E%3Crect%20x='28'%20y='176'%20width='264'%20height='96'%20rx='12'%20fill='%23ffffff'%20stroke='%23dbe3ec'%20stroke-width='1.5'/%3E%3Crect%20x='28'%20y='176'%20width='264'%20height='6'%20rx='3'%20fill='%232b86f0'/%3E%3Ccircle%20cx='58'%20cy='218'%20r='17'%20fill='%23e1eefd'/%3E%3Cg%20transform='translate(58,218)'%3E%3Cpath%20d='M8%20-2%20A9%209%200%201%200%206%207'%20fill='none'%20stroke='%232b86f0'%20stroke-width='2.4'%20stroke-linecap='round'/%3E%3Cpath%20d='M8%20-8%20L8%20-2%20L2%20-2'%20fill='none'%20stroke='%232b86f0'%20stroke-width='2.4'%20stroke-linecap='round'%20stroke-linejoin='round'/%3E%3C/g%3E%3Ctext%20x='82.0'%20y='214'%20font-family='Segoe%20UI,Microsoft%20YaHei,PingFang%20SC,sans-serif'%20font-size='15'%20fill='%231f2d3d'%20text-anchor='start'%20font-weight='700'%3E数字签名%3C/text%3E%3Ctext%20x='82.0'%20y='236'%20font-family='Segoe%20UI,Microsoft%20YaHei,PingFang%20SC,sans-serif'%20font-size='12.5'%20fill='%235b6b7b'%20text-anchor='start'%20font-weight='400'%3E需证书，可验证真伪%3C/text%3E%3Crect%20x='308'%20y='176'%20width='264'%20height='96'%20rx='12'%20fill='%23ffffff'%20stroke='%23dbe3ec'%20stroke-width='1.5'/%3E%3Crect%20x='308'%20y='176'%20width='264'%20height='6'%20rx='3'%20fill='%23155fc4'/%3E%3Ccircle%20cx='338'%20cy='218'%20r='17'%20fill='%23e1eefd'/%3E%3Cg%20transform='translate(338,218)'%3E%3Crect%20x='-7'%20y='-7'%20width='14'%20height='14'%20rx='2'%20fill='none'%20stroke='%232b86f0'%20stroke-width='2.2'/%3E%3Cline%20x1='-7'%20y1='-2'%20x2='-11'%20y2='-2'%20stroke='%232b86f0'%20stroke-width='2'/%3E%3Cline%20x1='-7'%20y1='3'%20x2='-11'%20y2='3'%20stroke='%232b86f0'%20stroke-width='2'/%3E%3Cline%20x1='7'%20y1='-2'%20x2='11'%20y2='-2'%20stroke='%232b86f0'%20stroke-width='2'/%3E%3Cline%20x1='7'%20y1='3'%20x2='11'%20y2='3'%20stroke='%232b86f0'%20stroke-width='2'/%3E%3C/g%3E%3Ctext%20x='362.0'%20y='214'%20font-family='Segoe%20UI,Microsoft%20YaHei,PingFang%20SC,sans-serif'%20font-size='15'%20fill='%231f2d3d'%20text-anchor='start'%20font-weight='700'%3E扫描件%3C/text%3E%3Ctext%20x='362.0'%20y='236'%20font-family='Segoe%20UI,Microsoft%20YaHei,PingFang%20SC,sans-serif'%20font-size='12.5'%20fill='%235b6b7b'%20text-anchor='start'%20font-weight='400'%3E图片型PDF先转成文字%3C/text%3E%3C/svg%3E)
对着自己的用途选一种，后面的步骤就不会白做。
第1步 先确认这份PDF到底能不能签
先摸清文件状态再动手，比签不上再回头查快得多。加过密、权限被限制的文档，点签名按钮不会有任何反应；扫描件也一样，整页只是一张大图，没有可以编辑的文字层。
具体操作
- 用阅读器打开 PDF，看标题栏或状态栏有没有出现锁形图标、「已加密」的提示。
- 点 文件→属性→安全，查看是否勾选了「禁止填写表单域和签名」。
- 点签字位置没反应，或者跳出来「此文档不允许签名」，说明权限被限制了。
- 扫描件、图片型 PDF 没有可编辑文字层，需要先做文字识别，转成可编辑 PDF。
- 右键 PDF→属性，确认没有勾选「只读」，否则编辑之后没法覆盖保存。
碰到这种文件，很多人会反复点签名按钮，或者干脆改后缀名，最后保存照样失败。顺序调一下就行：先看安全权限，再看是不是扫描件，最后检查只读属性。
'/%3E%3Crect%20x='28'%20y='64'%20width='262'%20height='142'%20rx='12'%20fill='%23fdeeec'%20stroke='%23e8604c'%20stroke-width='1.5'/%3E%3Crect%20x='28'%20y='64'%20width='262'%20height='42'%20rx='12'%20fill='%23e8604c'/%3E%3Crect%20x='28'%20y='94'%20width='262'%20height='12'%20fill='%23e8604c'/%3E%3Cg%20transform='translate(50,85)'%3E%3Ccircle%20r='12'%20fill='%23ffffff'/%3E%3Cpath%20d='M-5%20-5%20l10%2010%20M5%20-5%20l-10%2010'%20fill='none'%20stroke='%23e8604c'%20stroke-width='2.6'%20stroke-linecap='round'%20stroke-linejoin='round'/%3E%3C/g%3E%3Ctext%20x='70'%20y='91'%20font-family='Segoe%20UI,Microsoft%20YaHei,PingFang%20SC,sans-serif'%20font-size='15'%20fill='%23ffffff'%20text-anchor='start'%20font-weight='700'%3E误区%3C/text%3E%3Ccircle%20cx='50'%20cy='126'%20r='3'%20fill='%23e8604c'/%3E%3Ctext%20x='64'%20y='130'%20font-family='Segoe%20UI,Microsoft%20YaHei,PingFang%20SC,sans-serif'%20font-size='13'%20fill='%231f2d3d'%20text-anchor='start'%20font-weight='400'%3E扫描件直接盖章%3C/text%3E%3Ccircle%20cx='50'%20cy='152'%20r='3'%20fill='%23e8604c'/%3E%3Ctext%20x='64'%20y='156'%20font-family='Segoe%20UI,Microsoft%20YaHei,PingFang%20SC,sans-serif'%20font-size='13'%20fill='%231f2d3d'%20text-anchor='start'%20font-weight='400'%3E加密文件硬编辑%3C/text%3E%3Ccircle%20cx='50'%20cy='178'%20r='3'%20fill='%23e8604c'/%3E%3Ctext%20x='64'%20y='182'%20font-family='Segoe%20UI,Microsoft%20YaHei,PingFang%20SC,sans-serif'%20font-size='13'%20fill='%231f2d3d'%20text-anchor='start'%20font-weight='400'%3E只读文件直接改%3C/text%3E%3Crect%20x='310'%20y='64'%20width='262'%20height='142'%20rx='12'%20fill='%23e1eefd'%20stroke='%232b86f0'%20stroke-width='1.5'/%3E%3Crect%20x='310'%20y='64'%20width='262'%20height='42'%20rx='12'%20fill='%232b86f0'/%3E%3Crect%20x='310'%20y='94'%20width='262'%20height='12'%20fill='%232b86f0'/%3E%3Cg%20transform='translate(332,85)'%3E%3Ccircle%20r='12'%20fill='%23ffffff'/%3E%3Cpath%20d='M-5%200%20l4%204%20l7%20-8'%20fill='none'%20stroke='%232b86f0'%20stroke-width='2.6'%20stroke-linecap='round'%20stroke-linejoin='round'/%3E%3C/g%3E%3Ctext%20x='352.0'%20y='91'%20font-family='Segoe%20UI,Microsoft%20YaHei,PingFang%20SC,sans-serif'%20font-size='15'%20fill='%23ffffff'%20text-anchor='start'%20font-weight='700'%3E正确%3C/text%3E%3Ccircle%20cx='332'%20cy='126'%20r='3'%20fill='%232b86f0'/%3E%3Ctext%20x='346.0'%20y='130'%20font-family='Segoe%20UI,Microsoft%20YaHei,PingFang%20SC,sans-serif'%20font-size='13'%20fill='%231f2d3d'%20text-anchor='start'%20font-weight='400'%3E先看安全权限%3C/text%3E%3Ccircle%20cx='332'%20cy='152'%20r='3'%20fill='%232b86f0'/%3E%3Ctext%20x='346.0'%20y='156'%20font-family='Segoe%20UI,Microsoft%20YaHei,PingFang%20SC,sans-serif'%20font-size='13'%20fill='%231f2d3d'%20text-anchor='start'%20font-weight='400'%3E扫描件先转文字%3C/text%3E%3Ccircle%20cx='332'%20cy='178'%20r='3'%20fill='%232b86f0'/%3E%3Ctext%20x='346.0'%20y='182'%20font-family='Segoe%20UI,Microsoft%20YaHei,PingFang%20SC,sans-serif'%20font-size='13'%20fill='%231f2d3d'%20text-anchor='start'%20font-weight='400'%3E取消只读再保存%3C/text%3E%3C/svg%3E)
第2步 按用途选签名类型并准备好签名素材
签名按用途分三种：自己留档、发给对方看、需要防篡改和验真伪。个人签字用手写或电子签名就够；对外合同、要核对签署身份的，走数字签名。
具体操作
- 手写：白纸黑字写好后用手机正对拍照，再用图片工具裁掉背景，存成 PNG。
- 手写板或触控板：直接在签名面板里用鼠标、压感笔画笔迹。
- 电子签名：输入姓名→挑选字体→生成签名图，个人使用不需要证书。
- 数字签名：需要 CA 机构签发的证书文件（.pfx/.p12），或者 UKey 硬件证书。
- 签名图建议做成约 200×80 像素、背景透明，避免一大块白底遮住正文。
拍照转出来的签名，边缘常带一圈灰底，贴在白底文档上很显眼，透明 PNG 最干净。画质别压得太狠，签名缩小以后，笔画粗细直接决定还能不能认出来。
'/%3E%3Crect%20x='28'%20y='64'%20width='544'%20height='52'%20rx='10'%20fill='%23ffffff'%20stroke='%23dbe3ec'%20stroke-width='1.5'/%3E%3Crect%20x='28'%20y='64'%20width='8'%20height='52'%20rx='4'%20fill='%23155fc4'/%3E%3Crect%20x='44'%20y='76'%20width='28'%20height='28'%20rx='6'%20fill='%23155fc4'%20opacity='0.16'/%3E%3Ctext%20x='58'%20y='95.0'%20font-family='Segoe%20UI,Microsoft%20YaHei,PingFang%20SC,sans-serif'%20font-size='14'%20fill='%23155fc4'%20text-anchor='middle'%20font-weight='700'%3E1%3C/text%3E%3Ctext%20x='86'%20y='95.0'%20font-family='Segoe%20UI,Microsoft%20YaHei,PingFang%20SC,sans-serif'%20font-size='15'%20fill='%231f2d3d'%20text-anchor='start'%20font-weight='700'%3E软件层%3C/text%3E%3Ctext%20x='560'%20y='95.0'%20font-family='Segoe%20UI,Microsoft%20YaHei,PingFang%20SC,sans-serif'%20font-size='13'%20fill='%235b6b7b'%20text-anchor='end'%20font-weight='400'%3E编辑器里直接签%3C/text%3E%3Cpath%20d='M294%20118%20l6%206%20l6%20-6'%20fill='none'%20stroke='%235b6b7b'%20stroke-width='2'%20stroke-linecap='round'%20stroke-linejoin='round'%20opacity='0.45'/%3E%3Crect%20x='28'%20y='128'%20width='544'%20height='52'%20rx='10'%20fill='%23ffffff'%20stroke='%23dbe3ec'%20stroke-width='1.5'/%3E%3Crect%20x='28'%20y='128'%20width='8'%20height='52'%20rx='4'%20fill='%232b86f0'/%3E%3Crect%20x='44'%20y='140'%20width='28'%20height='28'%20rx='6'%20fill='%232b86f0'%20opacity='0.16'/%3E%3Ctext%20x='58'%20y='159.0'%20font-family='Segoe%20UI,Microsoft%20YaHei,PingFang%20SC,sans-serif'%20font-size='14'%20fill='%232b86f0'%20text-anchor='middle'%20font-weight='700'%3E2%3C/text%3E%3Ctext%20x='86'%20y='159.0'%20font-family='Segoe%20UI,Microsoft%20YaHei,PingFang%20SC,sans-serif'%20font-size='15'%20fill='%231f2d3d'%20text-anchor='start'%20font-weight='700'%3E图片层%3C/text%3E%3Ctext%20x='560'%20y='159.0'%20font-family='Segoe%20UI,Microsoft%20YaHei,PingFang%20SC,sans-serif'%20font-size='13'%20fill='%235b6b7b'%20text-anchor='end'%20font-weight='400'%3E手写拍照转透明底%3C/text%3E%3Cpath%20d='M294%20182%20l6%206%20l6%20-6'%20fill='none'%20stroke='%235b6b7b'%20stroke-width='2'%20stroke-linecap='round'%20stroke-linejoin='round'%20opacity='0.45'/%3E%3Crect%20x='28'%20y='192'%20width='544'%20height='52'%20rx='10'%20fill='%23ffffff'%20stroke='%23dbe3ec'%20stroke-width='1.5'/%3E%3Crect%20x='28'%20y='192'%20width='8'%20height='52'%20rx='4'%20fill='%236fadf5'/%3E%3Crect%20x='44'%20y='204'%20width='28'%20height='28'%20rx='6'%20fill='%236fadf5'%20opacity='0.16'/%3E%3Ctext%20x='58'%20y='223.0'%20font-family='Segoe%20UI,Microsoft%20YaHei,PingFang%20SC,sans-serif'%20font-size='14'%20fill='%236fadf5'%20text-anchor='middle'%20font-weight='700'%3E3%3C/text%3E%3Ctext%20x='86'%20y='223.0'%20font-family='Segoe%20UI,Microsoft%20YaHei,PingFang%20SC,sans-serif'%20font-size='15'%20fill='%231f2d3d'%20text-anchor='start'%20font-weight='700'%3E证书层%3C/text%3E%3Ctext%20x='560'%20y='223.0'%20font-family='Segoe%20UI,Microsoft%20YaHei,PingFang%20SC,sans-serif'%20font-size='13'%20fill='%235b6b7b'%20text-anchor='end'%20font-weight='400'%3E数字签名验身份%3C/text%3E%3Cpath%20d='M294%20246%20l6%206%20l6%20-6'%20fill='none'%20stroke='%235b6b7b'%20stroke-width='2'%20stroke-linecap='round'%20stroke-linejoin='round'%20opacity='0.45'/%3E%3Crect%20x='28'%20y='256'%20width='544'%20height='52'%20rx='10'%20fill='%23ffffff'%20stroke='%23dbe3ec'%20stroke-width='1.5'/%3E%3Crect%20x='28'%20y='256'%20width='8'%20height='52'%20rx='4'%20fill='%23a6ccf9'/%3E%3Crect%20x='44'%20y='268'%20width='28'%20height='28'%20rx='6'%20fill='%23a6ccf9'%20opacity='0.16'/%3E%3Ctext%20x='58'%20y='287.0'%20font-family='Segoe%20UI,Microsoft%20YaHei,PingFang%20SC,sans-serif'%20font-size='14'%20fill='%23a6ccf9'%20text-anchor='middle'%20font-weight='700'%3E4%3C/text%3E%3Ctext%20x='86'%20y='287.0'%20font-family='Segoe%20UI,Microsoft%20YaHei,PingFang%20SC,sans-serif'%20font-size='15'%20fill='%231f2d3d'%20text-anchor='start'%20font-weight='700'%3E硬件层%3C/text%3E%3Ctext%20x='560'%20y='287.0'%20font-family='Segoe%20UI,Microsoft%20YaHei,PingFang%20SC,sans-serif'%20font-size='13'%20fill='%235b6b7b'%20text-anchor='end'%20font-weight='400'%3EUKey与手写板%3C/text%3E%3C/svg%3E)
用「软领PDF阅读转换器」更省事
PDF编辑就在它的主功能里，签名素材不用来回导进导出，图片直接放进文档，拖动四角就能等比缩放，签完顺手存回原文件。同一份签名要挪到第二页、第三页，复制粘贴即可，不用重画一遍。
软领是知名国产软件品牌，20 年技术沉淀、服务千万用户；软领官网 wyouhua.com 直接下载，安装无捆绑勾选项。软件里有客服按钮可以联系真人客服，情况比较复杂时也有工程师远程协助。
第3步 在PDF编辑工具里把签名插进去
素材备好之后，插入本身只有几步。绘制、输入、导入图片三种方式都在同一个签名面板里，选完拖到位置就行。
具体操作
- 打开工具→打开 PDF→进入「编辑」或「填写与签名」面板。
- 点「签名」→「添加签名」，选择「绘制」「输入」或「导入图片」。
- 把签名拖到签字位置，拖动四角控制点等比缩放，别拉变形。
- 同一签名可以复制粘贴到多页；需要时插入日期域，例如 2024-06-01。
- 走数字签名时：先「放置签名域」，再从证书列表里选证书并确认。
签名一般放在落款行上方或页面右下角，别压到正文文字上。多页合同是只签最后一页还是每页都签，按对方的盖章习惯来定。
'/%3E%3Crect%20x='28'%20y='94'%20width='122'%20height='78'%20rx='12'%20fill='%23ffffff'%20stroke='%232b86f0'%20stroke-width='2'/%3E%3Ccircle%20cx='48'%20cy='94'%20r='15'%20fill='%232b86f0'/%3E%3Ctext%20x='48.0'%20y='99'%20font-family='Segoe%20UI,Microsoft%20YaHei,PingFang%20SC,sans-serif'%20font-size='14'%20fill='%23ffffff'%20text-anchor='middle'%20font-weight='700'%3E1%3C/text%3E%3Ctext%20x='89.25'%20y='138.0'%20font-family='Segoe%20UI,Microsoft%20YaHei,PingFang%20SC,sans-serif'%20font-size='15'%20fill='%231f2d3d'%20text-anchor='middle'%20font-weight='600'%3E打开PDF%3C/text%3E%3Cpath%20d='M154%20124%20l9%209%20l-9%209'%20fill='none'%20stroke='%232b86f0'%20stroke-width='3'%20stroke-linecap='round'%20stroke-linejoin='round'/%3E%3Crect%20x='168'%20y='94'%20width='122'%20height='78'%20rx='12'%20fill='%23ffffff'%20stroke='%232b86f0'%20stroke-width='2'/%3E%3Ccircle%20cx='188'%20cy='94'%20r='15'%20fill='%232b86f0'/%3E%3Ctext%20x='188.5'%20y='99'%20font-family='Segoe%20UI,Microsoft%20YaHei,PingFang%20SC,sans-serif'%20font-size='14'%20fill='%23ffffff'%20text-anchor='middle'%20font-weight='700'%3E2%3C/text%3E%3Ctext%20x='229.75'%20y='138.0'%20font-family='Segoe%20UI,Microsoft%20YaHei,PingFang%20SC,sans-serif'%20font-size='15'%20fill='%231f2d3d'%20text-anchor='middle'%20font-weight='600'%3E选签名方式%3C/text%3E%3Cpath%20d='M295%20124%20l9%209%20l-9%209'%20fill='none'%20stroke='%232b86f0'%20stroke-width='3'%20stroke-linecap='round'%20stroke-linejoin='round'/%3E%3Crect%20x='309'%20y='94'%20width='122'%20height='78'%20rx='12'%20fill='%23ffffff'%20stroke='%232b86f0'%20stroke-width='2'/%3E%3Ccircle%20cx='329'%20cy='94'%20r='15'%20fill='%232b86f0'/%3E%3Ctext%20x='329.0'%20y='99'%20font-family='Segoe%20UI,Microsoft%20YaHei,PingFang%20SC,sans-serif'%20font-size='14'%20fill='%23ffffff'%20text-anchor='middle'%20font-weight='700'%3E3%3C/text%3E%3Ctext%20x='370.25'%20y='138.0'%20font-family='Segoe%20UI,Microsoft%20YaHei,PingFang%20SC,sans-serif'%20font-size='15'%20fill='%231f2d3d'%20text-anchor='middle'%20font-weight='600'%3E插入并定位签名%3C/text%3E%3Cpath%20d='M436%20124%20l9%209%20l-9%209'%20fill='none'%20stroke='%232b86f0'%20stroke-width='3'%20stroke-linecap='round'%20stroke-linejoin='round'/%3E%3Crect%20x='450'%20y='94'%20width='122'%20height='78'%20rx='12'%20fill='%232b86f0'%20stroke='%232b86f0'%20stroke-width='2'/%3E%3Ccircle%20cx='470'%20cy='94'%20r='15'%20fill='%23155fc4'/%3E%3Ctext%20x='469.5'%20y='99'%20font-family='Segoe%20UI,Microsoft%20YaHei,PingFang%20SC,sans-serif'%20font-size='14'%20fill='%23ffffff'%20text-anchor='middle'%20font-weight='700'%3E4%3C/text%3E%3Ctext%20x='510.75'%20y='138.0'%20font-family='Segoe%20UI,Microsoft%20YaHei,PingFang%20SC,sans-serif'%20font-size='15'%20fill='%23ffffff'%20text-anchor='middle'%20font-weight='600'%3E保存并加密%3C/text%3E%3C/svg%3E)
第4步 保存、加密并确认签名有效
签完先别发出去。存成 PDF 而不是图片，签名才是可编辑、可验证的状态，截图发过去等于把签名变成一张死图。
具体操作
- 另存为 PDF 格式，不要导出成 JPG、PNG，否则签名不再可编辑。
- 点 文件→属性→安全，设置打开密码或权限密码，限制后续改动。
- 数字签名完成后查看「签名」面板，正常会显示「签名有效」。
- 签名之后文档如果被改动，面板会提示「签名已失效」，需要重新签。
- 发出去之前换一台设备打开，确认签名位置、清晰度和页数都对。
权限密码设完自己也得记住，每次打开都要输一遍；它只是限制别人随意改，和打开就报错的强加密不是一回事。换台设备再开一次花不了一分钟，能挡掉大部分排版错位的问题。
大家常问
扫描件PDF怎么加手写签名？
先在工具里做一次文字识别，把图片型 PDF 转成可编辑 PDF，再按导入图片的方式把签名贴上去。不做识别也能贴，但签名浮在整张图上，打印出来边缘容易发虚。
PDF加签名时提示「此文档不允许签名」怎么办？
说明文件的权限被限制了。点 文件→属性→安全，看是不是勾了「禁止填写表单域和签名」；带密码的文档要先去掉权限密码，才能进编辑状态。
PDF数字签名显示签名无效或证书过期怎么处理？
两种可能：证书过了有效期，或者签名之后文档又被改动过。向 CA 机构重新申请证书，或者让文件回到未修改的状态，重新签一次。
手机上能给PDF加签名吗？
可以，手机端的 PDF 工具大多支持手写和导入图片两种方式。屏幕小，定位和缩放不好控制，正式合同还是放到电脑上签更稳。
PDF加完签名后还能被别人修改吗？
能改，除非你设置了权限密码。普通手写和电子签名只是加了一张图，改完看不出来；数字签名不一样，文档一旦被改动，签名面板会直接提示签名已失效。
推荐阅读
PDF添加签名PDF电子签名PDF签名位置怎么调软领PDF阅读转换器 
提示