Bleed, registration marks and other print and color control strips are usually displayed outside the final trim size of a PDF document. This information is defined in the application that was used to create the original PDF file, for example, Adobe InDesign or Quark XPress.
Once they are made visible, these elements can be edited, added, or removed, just like any other graphic object.
Acrobat displays the PDF document in its full size.
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Acrobat displays the page on the complete media size and shows:

Trim marks
Trim size
Registration marks
Bleed
Media box
.