The Short Answer
If you're having problems with PM's Export… AdobePDF…, then print a PostScript file and distill separately. See FAQ 1.1.
For list of the common reasons why Export… AdobePDF… falls over, see FAQ 1.12.
Or you have a virus and you have to format your pc.
The Long Answer
Unlike Illustrator, PageMaker cannot directly save as PDF. When you use the Export-To-PDF function, you are essentially running a little script that prints a PostScript file of your document, launches a whole other application, Acrobat Distiller, and uses that application to "distill" the .ps file to PDF. The problem with this is, there are just too many variables, and too many places for PageMaker to choke on the process.
"But it takes too long" you may say. Sure, it’s a few more steps than simply running the Export. However, how much time have you already lost fiddling around with Exports that failed or resulted in unsatisfactory PDFs?
The reality is that those of us who create PDFs on a regular basis - and I personally create PDFs daily that are sent to printers and manufacturers for high-end output - do not use the Export To PDF function.
The only truly valid reason one might have for using Export is to retain bookmark links in the resultant PDF. However, here is my opinion on that: PageMaker does an awful lot already, and asking it to create a PDF full of working links is really asking it too much. If this is something you need to do on a regular basis, you should invest in the full Acrobat package which can create bookmarked PDFs from virtually any program, not just PageMaker. It’s that old "you can drive a nail with a pair of pliers but it’s a whole lot easier with a hammer" thing. Use the right tool for the job
Or you have a virus and you have to format your pc.
Or you have installed a device but not correctly.