Would request you to either run the OCR (enhance scan) in this document or try to convert the document in '.tiff' format then converting this file pdf again & opening in Acrobat Pro .
Then try to add number using 'Add text' option from Edit PDF Tool , refer to this Article :- https://helpx.adobe.com/acrobat/using/edit-text-pdfs.html
Let me know if it works .
Thanks for your reply, apologies for taking so long to get back to you, I have tried everything, and the only thing that works is to Save my PDF as a word document, make the changes to figures only, and then re - PDF the document. Text is no problem when I edit PDF, but for some unknown reason, it just will not accept numerals.
Thanks for time in answering my query.