Ability to use file as a background

[PerfectlyInternal]

Is your feature request related to a problem? Please describe.
I have a PDF template I use for each page of my notes. Currently, I need to import the template for each page separately, and then manually align it to the page. It would be nice to be able to import it once and have it be the background on every page.

Describe the solution you'd like
I want to be able to import a PDF (or any other file type) and use it as the background for every page in a document. (optionally resizing the page to fit the imported file)

Describe alternatives you've considered
One possible alternative is the ability to automatically resize and align imported files to page boundaries, since this is equivalent to my current workflow, just automated.