Guides

Rulers and Guides are useful for precise positioning of objects in a document
Rulers
To show or hide the rulers, go to View > Show/Hide Rulers in the menu or press CMD-R. Right-click to show the rulers context menu where you can add a new guide, change rulers status or change the document units.
Guides
To show or hide the guides, go to View > Show/Hide Guides in the menu or press CMD-;.
To lock or unlock the guides, go to View > Lock/Unlock Guides in the menu or press OPT-CMD-;.

To add a new guide:
  1. Click and drag from the rulers to create a new guide: dragging from the top left corner creates both a vertical and horizontal guide.
  2. Right-click anywhere and select "New Guide..." or double click on the rulers to create a new guide.
To reposition a guide:
  1. Click on a guide and drag it.
  2. Right-click on a guide and select "Edit Guide ...".
To delete a guide:
  1. Click on a guide and drag it out of the document.
  2. Right-click on a guide and select "Remove Guide".