When I open a pdf file, I would like to make a category to save a group in and then save them to this group--so, how do i save pdf files and how do I make a new category to save them too?
Thanks

I use iannotate, check it out hope this helps you out. 

If you open the PDF file in iBooks, then you can create folders there in which you can store the different categories of files.

If you've downloaded the PDF file using Safari then, when viewing the file in that app, if you touch the screen you'll see a menu at the top and there is a 'curly arrow' icon. If you touch that icon you'll be offered the option to open the PDF file in iBooks.

Tim

You can also get Goodreader ($4.99, USD). Once installed, you can save those PDFs to Goodreader, which is to the main, top level of the app. Then, you can open Goodreader and sort those PDFs into as many layers of folders as you wish.

Goodreader is very handy for file management, plus it reads PDFs quite well ... plus you can annotate on the PDF.

Thank you for all the replies.
Have downloaded Goodreader--works great!