Ensure the commenting toolbar is available (View->Toolbars->Commenting)
Click on Sticky Note () 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..., Infix Pro PDF Editor will now ask you to supply one
This user name will be recorded in each sticky note (or other comment) you make.