Word can check if you use a single or double space after a sentence (fullstop/period) but how can it be changed single space to double throughout a document?
The Sentence Spacing settings (single, double or don’t care) is in Word’s Grammar settings see Sentence Spacing in Word.
These days, sentences more commonly separate with a single space see Change to single sentence space after fullstop/period in Word
More care is necessary finding single spaced sentences because there may be double spaced sentences already. Searching for ‘period then space’ will find both single and double spaced sentences.
We need to turn to advanced Find/Replace with ‘Use Wildcards’ ON.
. ([0-9A-z]) – fullstop/period, space then ([0-9A-z])
The wildcard [0-9A-z] finds any digit or letter. Adding the round brackets saves the found character for use as ‘\1’ in the Replace statement.
. \1 – fullstop, space, space then \1
Repeat for sentences ending with a question mark ? or exclamation mark ?