I took an 845 pg document and converted it as save as other, selected image and then tiff. It gave me an error that Acrobat could not save a page in this document due to error "Expected a number object (Page 1)". I selected ignore and then it created 843 tiff files. Normally when I cannot OCR a document due to renderable text, I would take each tiff file and indivually converted them to pdf and then combine them back as one pdf. However when I did this step it only creating 843 tiff files, I found the exact page numbers that were creating the issue and corrupting my document. I printed those pages, scanned and then inserted them back to the pdf. Document is fixed! Lots of steps but I didnt lose my document.