When you open a publication, you'll see the publication toolbar.
You can display the toolbar by swiping in from the left side of the screen to the inside of the screen.
You can also add annotations to PDF documents.
Press 3 seconds on any place in a PDF document, and the Annotation Options will show. You can add a Note, a Signature, freedraw (Ink), Text and shapes (arrow, line, rectangle, ellipse) to the PDF.
Use the Share button () to send the PDF with the annotations.