🚀 go-pugleaf

It is important to understand what is actually in the PDF document. All that may be there are pictures of the pages rather than text itself. In this case, search is clearly much more limited.

You can usually determine this easily by trying to select the text. If there isn't any, you end up selecting the image of the entire page.

OCR in Acrobat can be helpful here, but as with all OCR, your mileage may vary.

The only reason I can think of for the file size to increase so dramatically after OCR is if the OCR success rate was very low and you end up with lots of images of the failed text. Whether this happens depends on the options and Acrobat version you use. Searchable Image may be the best OCR option, but regardless, if there is a low OCR success rate, searching won't work very well.