Reply To: GREP to search all end of paragraph without a full stop and add it automatically

Did you check whether there are any paragraphs that end in a space (or more spaces even)? If there are any they would trip up the solutions suggested above. To delete any trailing spaces, use this query:

Find: +$
Replace with: <leave empty>

And for sport here’s yet another query to find paragraphs that don’t end in a period and insert a period:

Find: (?<!\.)$
Replace with: .