Keep in mind that there are no perfect document accessibility checker solutions. It is always likely that one solution identifies an error that another solution might miss entirely.
Whenever possible, it is a good idea to use both the accessibility checker built into the native application of your document (e.g., Microsoft Office Word, PPT, or Adobe Acrobat). The more information you have to correct any issues you might have the better. For more information on how to use the accessibility checkers in Word, PPT, and/or Adobe Acrobat, see Creating Accessible Documents.