1. Run the latest version of Agile PDF Editor on the desktop. After opening the software, click the "File" option in the interface, and then click the "Open" option to open the PDF file.

2. After opening the PDF file, click the "Document" option, and then click the "Manage" option of "Signature and Abbreviation".

3. After entering the interface for managing signatures and abbreviations, click the "Add" option, and then click the "Draw Signature" option to draw a signature.

4. After entering the signature drawing interface, draw the signature to be added. After successful drawing, click OK to add the drawn signature to the PDF file.

5. Finally, save the edited PDF file.