Ensure the Commenting toolbar is visible (View > Toolbars > Commenting).
Click on the Sticky Note icon on the Commenting toolbar.
Drag out a box to denote the size of the new sticky note. Alternatively, single-click the left mouse button to create a standard-sized sticky note window.
If you have not already set up a user name using File > Preferences > Saving, FlexiPDF will now ask you to supply one: This user name will be recorded in each comment you make.
on the Commenting toolbar.