Don't expect a easy single pure Abap solution (only for text, with a good+ knowledge of pdf technical specification and link to some Adobe libraries) whatever the actual pdf contains (bitmap, compressed image, text blocks, tags, table) - google on Adobe forums...
Better look for add-ons/applications, is there already any OCR/dematerialization tool used for scanning received invoices or delivery documents letter, mail, fax from company as SAP/Open Text, Readsoft and many other in your system?
Regards,
Raymond