IrfanView (Freeware) can batch convert jp2 to any image format you like quite fast. You can then use the free jpg to pdf converter to turn the images into a pdf. (The converter is misnamed: you can use png files just as well). I've done it that way quite a few times, and it works nice and quickly.
https://www.irfanview.com/
http://www.freepdfsolutions.com/free...converter.html
EDIT: For reference: after I posted this, I started a conversion the way I described. 230 pages, the pdf file was ready three minutes ago, so those 230 pages took under twenty minutes. So your 745 pages should be done in about an hour.