For offical PDF documents (accounting, taxes etc) that have to be signed and dated and sent back, rather than printing and scanning them you can scan your signature and the date, turn them into a transparent png, then in Acrobat Pro:
- Choose Comment tab (注释，top right) > Click on the Stamp icon (like a blue hot air balloon)
- In the drop down menu that appears choose ‘Custom Stamp’ (自定义图章) > ‘Create Custom Stamp’ (创建自定义图章)
- In the window that appears, click the ‘Browse’ (浏览) button, note that in the next window that appears you have to click on the pull down menu to choose your file type, otherwise it will only show PDFs. Choose file type .PNG
- Once chosen you can move it around to crop it, click ‘ok’ then > Give it a ‘Category’ (种类), which would be ‘Sign Here stamp’ (在此签名图章), and name it something like ‘My signature’
- Now when you go back to the Comment > Stamp icon menu you should see your Signature png under the ‘Sign Here stamp’ menu and can place and resize it as needed. If a ‘Details’ window appears, you can fill it in or just click through.
To insert typed text, like the date, just click on the ‘T’ icon to the left of the Stamp hot air balloon.
For older versions of Acrobat (I think X and before, my original post on this was from 2012):
- Choose Tools > Advanced Editing > TouchUp Object Tool .
- Right-click the page and choose Place Image.
- Select an image file, and click Open.
Source: Adobe Help