PDF8: Providing definitions for abbreviations via an E entry for a structure.PDF7: Performing OCR on a scanned PDF document to provide actual text.PDF6: Using table elements for table markup in PDF Documents.PDF5: Indicating required form controls in PDF forms.PDF4: Hiding decorative images with the Artifact tag in PDF documents.PDF3: Ensuring correct tab and reading order in PDF documents.PDF2: Creating bookmarks in PDF documents.PDF1: Applying text alternatives to images with the Alt entry in PDF documents.