Add character count adobe acrobat

If there's a character limit to the field you'll find it under its Properties, in the Options tab:

You can increase that value or just tick off the check-box to disable this limitation entirely.

However, my guess is that's not the issue. Does it stop allowing you to enter more text when you reach the end of the field? If so, the issue is probably not a character limit but the font size. Either change it to Auto, or tick the "Scroll long text" box in the dialog above, and it will allow you to enter more text than what the field can show. The latter solution is not good if you want to print the file, though, as the overflowing text will not be printed. For that you should use the Auto font size, which will cause the font to become smaller as you enter more text, still fitting all of it in the visible area.