PDFSecure is a paid addon powered by WPDigiPro plugin so, you have to activate the license key first to use it.
Go to Dashboard > WPDigiPro > Settings > Add-on Licenses and activate the addon.
Once this addon is activated make sure while creating a product. You select, Yes as an option in Enable Licensing under License Settings. In case if you’ll select No as an option then, every attached PDF will be accessible without entering it’s encrypted key.
You’ll see a lock icon appearing next to the PDF file that you have uploaded. If you want the PDF to be password protected, click on the lock icon and it’ll be locked.
Any PDF file that you’ll upload in Deliverable Settings will be accessible by it’s license key only, which a user can find from their dashboard. (screenshot below)
Common Installation Problem
“Are you sure you want to do this?”
If you get the “Are you sure you want to do this” message when installing any .zip file via WordPress, it means you have an upload file size limit. Install the plugin via FTP if this happens, or ask your hosting company to increase the limit.