Import PDF into Persepective

Is it possible to import a pdf into perspective?
Client would like to have a section for device manuals.

Yes - you must use the File Upload component due to browser security restrictions, but once uploaded you can do whatever you want with the file on the gateway.
https://docs.inductiveautomation.com/display/DOC80/Perspective+-+File+Upload

Where does this file upload to on the Gateway?

You write a handler that chooses where to save the file, if at all. See the docs Paul linked to.