If you encounter the following error message when trying to open a PDF file, it means that your PDF viewer or browser does not support encrypted files:
The solution is to download and install the latest version of Adobe Acrobat Reader software, available for Windows and Mac OS. It is free and the only PDF reader guaranteed to open all PDF files, including encrypted ones. We thoroughly check every PDF file we create before providing it to you. Therefore, once you open it with Adobe Acrobat Reader, everything should work smoothly.
Here is how to open encrypted PDF files using Adobe Acrobat Reader:
Save the PDF file you want to open to your computer.
Right-click on the file and select Open with > Adobe Acrobat Reader.
Note: if you double-click the PDF file, it may automatically open with an out-of-date reader.