opening pdf documents within php

I'm creating a Content Management system in which the user will have to attach a pdf document to an article. This is no problem, I copy the document to a specific pdf folder and store the document name in the DB to use on the front end. On the front end I loop through all documents that are online and print the title, display pdf icon, print pdf name and description and link to the document (in the specific pdf folder) <a href='pdf/$pdf[$i]'><img src='images/icon_mini_pdf.gif' border='0'></a><i>$pdf[$i]</i> where $pdf[$i] is the pdf name (for each $i) I have tried this with a number of pdf documents, with certain documents I get parser errors! (Could there be problems with the document itself? On the majority I get the standard windows popup message asking to me to open online or save locally. If I open online nothing happens! Acrobat reader opens and then closes straight away! If I go to save, it automatically puts the extension html on the file name! If i change this to pdf I can save it ok and I can open it without problems. Are there certain options in the php.ini or Apache.conf file I need to enable to view pdf files in php? I have seen the extension ;extension=php_pdf.dll commented out. Anyone any ideas?