If you have uploaded PDC files to your web server but you cannot access them then the most likely reason is that you have a Windows server running IIS.
If this is the case then the file’s MIME type must be registered on the server before it will allow the file to be transmitted through the web server.
The procedure for registering a MIME type in IIS is given on following Microsoft pages:
For the extension type .pdc and for the MIME type PDC Viewer. Then restart the IIS server.
Another solution would be to use a file download script that would serve the PDC/LLV files with the correct MIME type. For example, Zubrag Smart File Downloader.