Guide on Reader app's ease of use

Are you referring to Adobe Acrobat Reader or another application by which you ascribe the otherwise vague "Reader" term?

If Adobe Acrobat Reader, then there are two menu items on its Help menu for user orientation of the application. That is as good as it gets. Ease of use is typical Adobe, with many shown features that require Acrobat subscription services. PDF searching and annotation capabilities are more advanced than Apple's Preview, with much better PDF handling in cases where Preview won't process the PDF.