Download a file manager app like Pocket File Manager and save it to a folder accessible by your PC. When you open the file directly with a PDF reader app, it is stored in the app's storage and can only be accessed by the app.
i.e. - When I click on a PDF attachment, it asks me what I want to use to open it. I select Pocket File Manager, which, in turn, asks me where I want to save the file. I select my documents folder. I then plug my phone into my PC and access the folder in File Explorer and print from there.