1. Download WPSoffice and document management APP on your mobile phone. Open a PDF file in the mobile phone document. 2. When opening a file, there is a default reading mode, which can only be read. There is also an editing mode, click on the tip shape in the upper right corner. 3. In edit mode, there are many functions at the bottom of the file. Choose Insert-Signature. This sharing is to insert signatures, and sometimes I work outside for the convenience of signing. After entering the signature, you can see that I haven't added the signature yet. You can click here to add a new signature.