Our plugin has been tested on PDF forms with over 700 fields. However, the PDF form must be Adobe Acrobat Form compatible, and the size of the PDF form should not be more than 5MB. Larger files are possible, however, they are slow and require PHP settings to be changed.
We STRONGLY recommend naming the PDF form fields EXACTLY the same as the Formidable Form “KEY” values (not the field ID or field name), then use the “Enable automated layout creation for new field maps” setting on the SETTINGS tab to auto-create the Field Map Layout. (you’ll still need to map each checkbox field)