File Download and Run the PDF Unlocked file from Adobe Support Community if you have one. This file shows that Adobe Reader is using the latest update, and it is protected to prevent other applications from interfering with it. Download and Run the PDF Unlocked File Now, you can open the protected PDF file. It's a PDF document, so it's in a PDF format. Once it opens, then it opens automatically with Adobe Reader. This is a good time to go back to the Adobe Reader site and download and install the update. To do this in case you get any PDF not running on start up, you can use these following steps: Download the latest Adobe Reader update and install. Step 2: Open Adobe PDF Reader. At the top is a drop-down menu, click to show the Compatibility View. You can use this menu to check the protection of the PDF file. If it warns you of a threat to the contents, just click “Yes”. If it warns of some kind of restriction on the contents, just click “Yes” to proceed. If it's OK, then you can proceed to the next step. This is an Adobe Reader update. You can still download and use the older Adobe Reader from Adobe Support Community. However, it won't be able to open the protected PDF files because they are protected with an update or Adobe has already blocked them. This is a temporary step to check if the Adobe Reader installation is properly working.