If you are working with Adobe Acrobat Pro, there is a certain way to save your PDFs so that they can be opened in older versions of Adobe Reader. If you don’t use this, the user will most likely receive an error. Follow the instructions below.
Work with older versions of Adobe Reader
In the menu, go up to File > Save As.
Then select Reader Extended PDF > Enable Additional Features…
Your PDF should now be readable by older versions of Adobe Reader.