1. A computer-implemented method of annotating pages of an electronic document independently of the contents of the electronic document, the computer-implemented method comprising the steps of: displaying a page of the electronic document on a computer display device using a document browser that permits a user to move forward and backward among a plurality of document pages; detecting a selection of an annotation mode that permits the user to annotate the currently displayed document page, wherein at least an ink annotation mode, a highlight annotation mode, and an eraser annotation mode are provided as options from which the annotation mode is selected; receiving annotation stroke input from a user input device indicating movement associated with the user input device for a continuous distance about a stroke location on the currently displayed document page; storing annotation stroke data based on the received annotation stroke input, said annotation stroke data comprising data corresponding to the stroke location and the movement associated with the user input device, wherein the annotation stroke data is stored in an annotation file associated with the user, the annotation file stored separately from the electronic document; storing annotations made in the highlight annotation mode as a bitmap image; and blending pixels in the annotation file with pixels in the electronic document to cause the computer display device to display the electronic document with annotations.