What is Adobe Acrobat and why do I need it? Adobe Acrobat Readers allows you to see files with a .pdf file extension. These files are formatted just like a paper document. Some of the files on the Engineering Web are in this format. Unfortunately, your browser cannot interpret these files without the Adobe Acrobat Reader, which is available free of charge at http://www.adobe.com/prodindex/acrobat/readstep.html.