You can utilize the tools in the toolbar to navigate the document and switch among different modes while you're reviewing a document using the Document Markup tool.
The introductions for each icon (from left to right) are described as below:
Save: Save all your edits (annotations/custom stamps/etc).
Download: Download the document along with all available edits. A window will pop up to ask you to fill in the file name and specify the destination format and range of pages.
Print: Print the document. A window will pop up to ask you to specify the destination, the content to print and the range of pages.
First Page: The first page of the whole document.
Previous Page: The previous page of the current page.
Page Number: Current page number / total number of pages.
Next Page: The next page of the current page.
Last Page: The last page of the whole document.
Next Page: The next page of the current page.
Zoom In: Zoom in the entire document.
Zoom Out: Zoom out the entire document.
Page Rotate Left: Rotate the current page 90 degrees left.
Page Rotate Right: Rotate the current page 90 degrees right.
File Rotate Left: Rotate the entire document 90 degrees left.
File Rotate Right: Rotate the entire document 90 degrees right.
Toggle Page View Mode: Toggle between Single Page view and Full Document view.
Mouse Mode: Toggle among Pan, Select and Zoom mouse mode.
Zoom Mode: Toggle among Fit Width, Fit Page and Fit 100% zoom mode.
Full Screen: View the document in full screen.
Custom Stamps Management: Go to the Custom Stamps Management page.
Reset Annotations "Show Again" Property: Reset the "Show Again" property of all annotation tools.