Adobe Reader is a free program offered by Adobe, that allows users to read PDFs. However, it cannot edit them, at least not for free!
Adobe Acrobat DC
Adobe Acrobat is a paid-subscription product that allows users to read and edit PDFs.
How Do You Set One As Your Default Program?
For Windows Users (10 and 11):
Right-click the PDF, choose ‘Open With’, click ‘Choose Default Program’, and then select your preferred PDF program from the list it provides. (If you have both Adobe Acrobat Reader DC and Adobe Acrobat DC, you should generally select Adobe Acrobat DC – it has more features!) If you want it to always use the program you’ve picked, select the checkbox at the bottom that says “Always use this app to open .pdf files” at the bottom, and hit ‘Okay’.
For Apple Users:
Click the PDF file’s icon in the finder to select it. Go to ‘File’ in the top left, and select ‘Get Info’. Click the triangle next to ‘Open With’ to open the dropdown menu of programs, and select your desired program from the list (if it’s not there, it may be available under the option for ‘Other’). Click ‘Change All’.