Now this only happens with some files. when I try to make a PDF it will get stuck on "it says ploting viewports" and when I try to click on any thing it will say not responding and crash. How can I fix this problem. 

what pdf creator are you using? Try CutePDF, good tool

You need to install adobe acrobat and when you need pdf file from dwg you just print dwg out. On printer name you will see printer name adobe pdf. You just print it out by use that printer.http://gizmeau3d.multiply.com3d architectural rendering service

+1 for CutePDF...Which version of AutoCAD and how big is the drawing file?