When you place the cursor in front of the symbol, a hidden frame will appear. This is an indication of the space provided on the original form. Tabs are allowed in side the frame. If you over run the frame space, you may have to adjust pagination. I have not figured out a way to check the check boxes.
Some forms contain tables.
You can use tabs or mouse to get from one cell to another. If you wish to tab with in a cell, use ctrl-tab. When you see a non printing space symbol, place the cursor to the right side of the symbol before entering data. The symbol marks a font change.