I currently created a form in which one to three users use the form to fill a report. User one will fill the section belonging to them and the next user will do the same. To prevent any work done by the previous user from being deleted I have a submit button to flatten the pdf. There are no fields as the users just jot down notes. The issue here being that the button flatten with the rest of the page. Is it possible to protect a previous user's work without disabling the submit button.
You can flatten individual pages, instead of the entire document. Will each user only add comments to specific pages? If not, it will be tricky to achieve that.
Have you considered just marking the filled in fields as Read-only instead?
You can also flatten specific form fields based on the visibility settings. However, flattening only works in Acrobat Pro. If this form is to be used on Acrobat Reader, it would be better to mark the fields as readonly.