An imprint is an object such as an annotation added on top of the existing PDF page that can be edited, moved, resized, etc. When "editing" original PDF text and images in a document, parts of the page are removed and replaced by imprints to match the original. As you edit the PDF content, you are editing these imprints. An exception is when using the Precision Edit tool
to move objects. In that case, the original objects are moved.

Imprints are rendered into the drawing layer of a document. Other PDF editors won't be able to edit the imprints unless they are capable of manipulating the content of a document. For example, Preview and Acrobat Reader can manipulate annotations such as Comments
, Notes
, and form fill-ins, but not imprints or other document content.

In PDFpen, use the Precision Edit tool 
to select and edit line art, which includes certain borders and registration marks found in documents. The Edit tool
can only select and edit images. (Editing bar).