If you have Adobe Acrobat Pro, you can
1) Open the pdf;
2) Click on the Scan & OCR tool;
3) Click on Recognize Text;
4) Choose “Hebrew”
5) And then click on the Recognize Text button.
Adobe Acrobat Pro will convert the words to digital format. If it’s a scan from a book, you will probably have to go through it and do a lot of corrections.
This may not be the best option, but it works to some degree.