Edit PDF adds new content on top of a page: text in Helvetica, Times or Courier with the size and color you choose, PNG or JPG images, shapes like rectangles, ellipses, lines and arrows, and freehand drawing. You can move, resize and delete what you added. It does not change text that is already in the PDF, so to correct a word, cover it with a white rectangle and type over it.
Annotate PDF is for reviewing. Highlight text by selecting it or freehand, add text notes, draw, and insert an image or stamp. Annotations are saved in the standard PDF format, so they appear in Acrobat, Chrome, Edge and most readers, where they can still be edited or removed. PDF Forms fills existing form fields (text, checkboxes, options and drop-down lists) and lets you draw new fields on the page; it can also flatten the form so it can no longer be changed.
For page layout, Rotate PDF turns all pages or only some by 90° or 180°. Crop PDF lets you draw the visible area and apply it to one page or all; what's outside is hidden but still in the file, so use Redact PDF to truly remove information. Page numbers adds numbering with your choice of position, format ("1", "1 of N", "Page 1" and more), starting number and page range, so the cover can stay unnumbered.
Watermark stamps text or an image on the pages, with opacity, rotation, one of nine positions or a repeated tile pattern. Edit PDF Metadata changes the title, author, subject and keywords, or clears them all, which is useful so the title displays correctly and your user name isn't left in the file.
Two tools change the whole document at once. Resize PDF puts every page on A4, Letter, Legal, Oficio México, A3, A5 or a custom size, scaling the content without distortion and keeping each page's orientation; the PDF to Letter size and PDF to A4 pages start with those sizes. Grayscale PDF turns every page into shades of gray at 150, 200 or 300 DPI, keeping the selectable text in an invisible layer, so you can print without color ink or pay the black and white rate at a copy shop. Both drop links and form fields, and in Grayscale PDF the pages become images.
A few combinations come up often. To prepare a report, add Page numbers and then a Watermark marked "Draft" or "Confidential". To return a form, fill it with PDF Forms, add your signature with Sign PDF and flatten it. To review a contract, use Annotate PDF to highlight clauses and leave notes for the other side, who can see and remove them in their own reader.
Make PDF look scanned gives a digital file the slight tilt, grain and paper tone of a scan, subtle, normal or heavy, in color or black and white. It is meant for cases such as an office that asks for a scanned copy of a document you already signed on paper, not for passing one document off as another. Each page becomes an image, so the text is no longer selectable and links and forms are lost.
When the edits are final, Flatten PDF fixes annotations and form fields in place, and Protect PDF adds a password.