Why not add a PDF item to the list so you don't have to manually enter it? It seems to me that PDF files are too important to overlook to require a manual entry.
Best answer by JimM
In the short term, anyone looking to backup a PDF file should create a filter. Here is how:
To make a filter, open Webroot, and go to Backup & Sync. Click "change settings" on the Backup area of the screen.
Click "Add Filter."
Choose the directory you want your pdf files to be backed up from on the Directory line. On the Filter Name line, name it whatever you like (I use "PDF Files" in this example). The most important part is that on the "File type expressions" line, you'll want to put *.pdf Then click "Save."
The same procedure can be used for adding any file type as a filter for backing up that kind of file. Just replace *.pdf with whatever extention you're planning to back up.