A new post-it type is available (version 1.13). Its width and lenght are fully customizable to offer you more flexibility. It is also ideal for long texts.
Select the "free size" shape.
Open the post-it edition window (click on edit in the menu or double click on the post-it). Then select "free size" within the shape drop-down menu.
Edit a free size post-it.
Use the handle around the post-it to freely resize it in two dimension (height and lenght). The corner handles allow a free resizing in two directions simultaneously while the handles along the sides alow to resize in one direction only (width for the vertical sides and height for the horizontal sides).
As for the other features of the free size post-it, they are the same as for others post-its (see : Create and edit post-its).