I am currently using an older version [v.11 - Professional Edition] of the Abbyy FineReader OCR software to render text for several thousand PDFs. The software does something which I have found to not be possible with Adobe Acrobat Pro or version 12 of the FoxIt PDF Editor software. It will successively pick up a check mark or 'X' in a check box.
The software often gets the mark perfectly as:
[X]
. . . but will sometimes substitute a 'K' or if there's a check in the box:
. . . it will enter a minuscule character like this: ø
An empty checkbox may get converted to an 'n' or just an empty box: □
But it interprets the marks consistently so if you're analyzing thousands of documents you can successfully track when checkboxes were ticked off.