Conversions are not good for editing except on the most rudimentary level. The formatting of converted documents will be very poor even if they look good.

At least that part of the pdf may be from scanning rather than conversion and may not have been run through optical character recognition (OCR); that may have been needed.

Check with your client on the source of the pdf. If source is a Word document, try getting that rather than the pdf. If source is scanned material, ask client to run through OCR in Adobe Acrobat or some other program.