What is the maximum word count ProWritingAid can check?

There is no maximum word limit, however, requests over 150,000 characters (about 30,000 words)  are broken down into sections.    

This is done by chapter if the document includes chapter headings, or into chunks of 100,000 characters otherwise. 

Please  bear  in mind , our app works best when looking at fewer than 10,000 words at a time. This is because we have numerous high-powered reports which must contact our servers to function. Many customers break their documents up by chapter to get under that word count and to avoid becoming overwhelmed with suggestions.