If you have an older version of Adobe Acrobat, you may be having trouble opening newer PDF documents. That is because the newer formats aren't always consistent with older Adobe programs. You can re-convert a PDF file so it is compatible with an older program version as far back as Acrobat 3.0 using Adobe's Create PDF tool.
Convert the PDF file to a JPG image or EPS format. You can do this using Adobe Photoshop or by opening the file in a newer version of Acrobat (preferably version 7.0 or later). In Photoshop click "File" then "Save As" and choose .jpg from the list of options. In Acrobat select "File," "Export" then "Postscript" and choose "Encapsulated Postscript," which is the full name for an EPS file.
Go to CreatePDF.adobe.com. This is Adobe System's official online PDF creation tool. Create an account, verify your email as instructed and log in to the tool.
Find the JPG or EPS file on your computer, select it and click "Continue."
Select the older format that you want to convert the PDF file to under "PDF Compatibility" on the next page. The available options are Acrobat 3.0 (PDF version 1.2), 4.0 (PDF version 1.3) or 5.0 (PDF version 1.4).
Adjust your "Optimization Settings" if necessary. For instance, you can optimize the PDF for web or print viewing—the web option has compressed images while the print version is usually a larger file with high-resolution images.
Choose your delivery method. You can wait for the conversion to take place within your browser or have it emailed to you when the conversion is complete. Click "Create PDF" and wait for the file to convert.
The Create Adobe PDF site allows you five trial conversions so that you can get familiar with the tool. Thereafter you must pay for a subscription to the service. Some third-party software programs like the one offered by PlanetPDF.com will also convert a newer PDF file to an older format.
If your PDF file has multiple pages you may have to convert each page to JPG or EPS format then to the older PDF version individually, which can be very time-consuming depending on the length of the PDF document. You can compile the pages into one file again using Adobe Acrobat.