What does Adobe Acrobat Reader do well? - allows viewing and converting PDF documents, this so popular format across the globe - it is easy to use - has a graphical interface exactly the same in all the operating systems - it is a lightweight software - it is free
What does Adobe Acrobat Reader not do well? It doesn't allow to edit PDFs. :) For documents with images, the tool can become really slow, depending on how many images are embedded in the PDF.
What do you wish you had known about Adobe Acrobat Reader before using? Nothing, it is the go to software for reading PDFs and converting to PDF format. The drawback is that this tool allows only viewing/converting pdf files. If you need to edit, than you need to purchase the paid version from Adobe.
Have you used a competitor to Adobe Acrobat Reader? If so, how does it compare? Microsoft Word also can read PDF, however it is converting it to doc format and messes the document. If really needed you can use Word for viewing and saving to PDF format. In my view there is no competitor for Adobe Acrobat Reader because it is perfect for viewing PDF files.