General tab


Open the most recent file on startup
Allows you to automatically load the most recently opened or saved PDF file when the application is launched. Toggle it On or Off using this checkbox based on your preferences.

Units
Allows you to specify the preferred unit of length measurement.
For the print option, this sets the default paper size to either A4 for Millimeters or Letter for Inches.

Merged PDFs File Name Format
Allows you to specify the file name of the output file when merge PDF is performed. Include %autonumber% in the file name which will be converted to a unique number each time merge PDF is performed to ensure the output file name is unique.

Auto-save Interval (in seconds)
Allows you to specify the time interval (in seconds) that auto-save is performed once an update is done on the open PDF. Auto-save allows you to retrieve your updates on the file in case PicoPDF terminates abnormally. The prompt to retrieve is done the next time PicoPDF is started.