Quick question - when you say "set up a discussion but the discussion doesn't allow uploads of PPT or PDF files", are you talking about forums? They do allow such uploads, but it might be your max upload size is not big enough to allow uploads of large power point files. YOu could check this in the forum settings and also the course settings (and check with the admin)
Do you know what version of Moodle you are using? Go to a page where you have teacher editing rights and click the "Moodle docs for this page' link at the bottom - it should tell you a number which is the number of your version of Moodle.