if l buy a book,say the DMG,PHB,XGtE,Hord of the dragon queen,ect. is a pdf provided or is it just access to viewing it on the site? Am l  (legally and within the guidelines) able to make a personal copy for use off line?  (obviously l wont sell it or give it to anyone,but if something happens to my account,or this site goes under,l dont want to be out 1K with nothing left,so l figured there is no harm in asking these questions before buying.)

(sorry if this is in the wrong sub,this is the best fit l could think of.)

You get only access of dndbeyond site content. No pdf version. And you get all the contents for the dndbeyond tools.

If you want to copy/screenshot rules for your own use, nobody is stopping you.

There is a free mobile app that lets you download the “books” and read them off line. But no pdfs. 

I bought a few things so I could search them but I'll never not buy real live books.

I’ll never buy hard copy again. Between this site and the app there’s just no need to kill the trees anymore.

I am ok with trees serving my purpose.

Me too, like making breathable air for me to breath.

In my country we have sustainable forestry so you can have both

Quote from ArwensDaughter >>

There is a free mobile app that lets you download the “books” and read them off line. But no pdfs. 

 is it a dnd beyond app? if not,what is its name?

Quote from DnDNewper >>

Quote from ArwensDaughter >>

There is a free mobile app that lets you download the “books” and read them off line. But no pdfs. 

 is it a dnd beyond app? if not,what is its name?

 Yes, it is the DDB Compendium app.