On the sidebar, from top to bottom, it shows Thumbnail, Annotation, Outline, Bookmark.
You can see all the pages of the current document in a list of thumbnails in this tab, so you can easily jump between pages while you are reading the document.
You can find all the annotations (highlight, underline, strikeout, etc.) and comments you made throughout the document, so it’s easier to jump between them when you want to quickly review the document.
Click or and you can Import Annotations from other files or Export Annotations in the PDF and save as .XFDF files.
To delete annotations, tap or right click and choose Delete Annotation or Remove All Annotations.
If the document you are viewing has an outline, it will be shown here. Then you can navigate the whole file through the outline.
If the document does not include an outline, this tab will appear blank.
In the bookmark tab, all the bookmarks you set in this document will show here.
To add a bookmark, on the page you would like to bookmark, select Tools and tap on the toolbar. A dialogue will appear for you to name this bookmark. The default name of the bookmark will be the Page No, you can rename the bookmark by typing in a new name.
To sort bookmarks, tab . You can sort by Date created, by Name, or by Page.
To delete bookmarks, tap and choose Delete Bookmark or Delete All Bookmarks or you can tap and choose Yes in the pop-up window.