Sorry, can you clarify the question? When you say "session" do you mean a single window, which would mean you are putting several individual pages into one pdf? Understanding your question may help us find you an answer.
Are you referring to Adobe Reader or Adobe Acrobat? You cannot combine pdfs with Reader, but it is simple to do with Acrobat. Here is a site that walks you through several different ways to accomplish what you need.
Thanks for the link ... that is the questin in Reader being able to open multiple documents in one window.. not combine or edit just view .... seems a dumb thing to remove from the functionality of an upgrade ...
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