User needs to parse native-pdf(selectable data, not scanned, no OCR required) in local. The pdf files may be over 400 pages with large tables. Some tables may not have clear borders. Is there any API I could use? Thanks!
Now that I know you don't want an API, I might recommend that you check out ItextSharp, from nuget. I have used this several times in the past, and there are many stack overflow forums on how to use it. https://www.nuget.org/packages/iTextSharp/5.5.13.1
EDIT: I apologize, it looks like iTextSharp has been replaced with iText 7 https://itextpdf.com/en/products/itext-7