Editing PDF files in such a way should be avoided as much as possible. They were never meant to be edited like that.
The solution is to go back to the original file format used to create the PDF, edit it and then generate a new file.
If you don't have access to that file you can try exporting the PDF to a more editable format (Word, InDesign, etc.) and then work on it, but it's a long-shot...
How can you export to MS Word? Is there a function within the Acrobat interface?
File - Save As Other - Microsoft Word