Preview bug with PDFs and text

I just upgraded to El Capitan from Mavericks. (Yes, I know, I like to wait a while to ensure all bugs are ironed out...) But I I have a bug which is driving me mad. I used to be able to extract text from a PDF using the paid for app To Text Converter, but when I used this certain letters (i,f and l) are missing rom exported text. So I downloaded and paid for Filejuicer. Same thing. Now I have spent quite a bit of money. Grrrr.

So I make my own Application using Automator (wish I had done this in the first place as it only took two minutes and cost me nothing) and still the same problem.

So highlighted some text in a PDF and copied and pasted it into a Text document and still the same issue.

So I guess it's a problem with Preview, PDFs and El Capitan.

Anyone know of a fix (please don't say upgrade to Sierra as my Mac is so old now it won't support it.)

Thanks to all who may reply...