Open a QQ browser, click File to open a PDF document that needs to be signed, click Mark/Fill at the bottom of the document to enter the editing interface, select a signature, click New Signature to enter the signature writing interface, and click OK after writing.

Another advantage of using the browser to open the signature is that the next time you need to sign, you can directly click on the signature record to select the historical signature, provided that it has the same name.