This could be a problem with the browser not recognising the pdf file. I've had this problem before with IE - sometimes it opens the pdf properly, sometimes it displays the pdf code (the actual file data) rather than the pdf in acrobat, and sometimes just a blank page.
What happens if you right click on the links and save the pdf they link to rather than browsing to them? Do they work ok then?
You could try making a php script that outputs a header and then the pdf document, rather than just directly linking to the pdf, eg:
File: getpdf.php, gets called with an argument for the pdf to get:
http://www.yoursite.com/getpdf.php?pdf=thepdffilename.pdf
getpdf.php:
if( isset($_GET["pdf"] ) ){
$pdf = $_GET["pdf"];
/* for security, query your database to make sure this pdf file actually exists
maybe check the $pdf filename to make sure it is not 'dodgy'
*/
$ok = preg_match('|^[a-zA-Z_]*\.pdf$|'i, $pdf);
if( $ok ){
header("Content-Type: application/octetstream"); // force a 'save as' dialog box
readfile("/path/to/pdfs/$pdf"); // output the pdf file
exit();
}else{
echo "Sorry, $pdf is not a valid file.";
}
}else{
echo "Please go back to the list of pdfs and choose one to download.";
}
Hope this helps, Sam