If the PDF contains selectable text then the 'copy all to clipboard and then parse' technique Michael mentions is an option. The advantage is that the data will be 100% accurate (because it's not being interpreted by OCR), the disadvantage is that it may be hard to devise parsing logic that will work on all your files - it depends how the pages have been arranged.
There are 3rd party libraries that can extract text from PDFs (PDFPig for example) but these too can struggle to supply text in a consistent format/structure.
If the PDF text is not selectable, ie the file is a scan/image of text, then OCR is the only option. And because OCR is an interpretation dependent on the image quality, there is always the chance of a mistake and the ones you mention such as zero and capital o are typical. Note that MS Word also uses OCR to open such files and is also subject to similar issues.
You could apply 'post-reading' clean up rules, eg if you know a value cannot possibly contain $ then you could assume to replace it with S. Similarly if a numeric field is read as capital 'o' then you could assume it should be a zero. But such rules can only take you so far and you have to be very confident in your assumed substitutions. The Character Whitelist input can be used in a similar fashion - if you know you are reading a currency field then the whitelist might be $01234567.89
The Scale parameter can really help, but it's not the case that 'bigger is better' - sometime you have to experiment by incrementing the scale until you find the optimum value. You often find that quality decreases after a certain point.
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John Carter
Blue Prism
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