Im sure this is a simple process but I can't get it.   A friend emailed me link to a pdf file for a book.  I downloaded it and am enjoying the book but I can't figure out how to set a bookmark so I don't have to start searching from the beginning of the book each time.  The only option I see is to click the upper right hand corner, and click on bookbmarks, which takes me to a page that allows me to go to a specific chapter, but not page.   Help,  please.