The Adobe Acrobat Reader is a free PDF reader that allows for reading, copying, printing, and basic annotation of PDF files. It also allows the user to open encrypted for write-protected PDF files. One popular use is to fill out pre-made forms that are generated using Acrobat Pro. Acrobat Pro or a comparable PDF authoring program is necessary to create or change structure within a PDF.
Adobe Acrobat Reader is available on MacOS and Windows.