Revu has a number of Snap options that allow you to more accurately place markups and measurements on a PDF. However, if you don't know that one of the options is enabled, your mouse cursor may appear to jump, move unexpectedly, or select the wrong point.
The buttons to enable and disable Snap options are in the Status bar at the very bottom of the Revu window. Each button is highlighted when it is active. (Press the F8 key to display the Status bar if it isn't currently displayed.)
There are six buttons in the Status bar: Grid, Snap, Content, Markup, Reuse and Sync. It is important to note that Grid, Reuse and Sync do not have snap functionality; however, they all relate to markup placement and are therefore important to discuss.
Grid: Displays grid points on the PDF page, but does not snap to them.
Snap: Cursor snaps to the nearest grid point, even when the grid is not displayed.
Content: Cursor snaps to the underlying content of the PDF. A small blue-filled square cursor will display when it is near a point that it will snap to. A square (without the blue fill) will display when the cursor is near an object that it will snap to.
For example, the image below shows the cursor when a Length measurement is snapping to a point:
Markup: Snaps to other markups in the PDF, just like Content snaps to PDF content. Also displays horizontal and vertical "construction lines" that allow you to snap to the horizontal or vertical location of points on other markups, even if they are not currently displayed.
The Markup snap is very useful when creating forms.
Snap to a point
Guidelines creating a Polygon
Guideline creating aligned Rectangles
Reuse: Enables the same tool to be used multiple times without having to reselect the button on the toolbar. This mode is helpful when adding the same markup onto the PDF multiple times.
Sync: Synchronizes the display of split views when viewing the PDF using the Split View modes.
The Markup button and construction lines were introduced in Revu 9. Previously, there was a single Content snap that controlled both Snap to Content and Markup.