Justification changing when editing pdf

Hey there, so this morning while editing a pdf, I was trying to remove the apostrophe from "it's", and whenever i did so, that line, and the line below it, changed word spacing and moved beyond the justified margin, becoming flush with the bounding box.

For example:

The rest of the paragraph

was aligned neatly like so

but  the  edited line jutted out

like this, beyond all other text

so  that  now  it looks odd

How do I realign specific lines individually? Or alternatively, how do i turn off automatic formatting so that the spacing doesn't go haywire whenever I make minor edits?

(FYI, I do not have access to the original pre-pdf file, as prior edits were made by a publishing company using "pitstop". There is no word file.)

Thankyou!