Scan and OCR is not recognizing text on my document

I really need help figuring out this problem. Sometimes the OCR works and othertimes it doesn't. I'm trying to edit multiple, ( multi page pdf documents). I used scan and ocr for my last document and everything went through really easily. I'm able to click on the letters and easily delete and edit them. On other documents ive tried doing this to it doesnt work. It creates text boxes for the text that are all messed up and hard to edit. I'm not sure how to fix this as i've tried researching how and can't find any answers. My document itself is very clear and the same as the last one.