Congratulations Iconio.
I like all your products. I have screen calipers from the first version.
I got this new Screen Tracing Paper software,it's easy to use and simple to understand.
Just one remark; I think there was something missing, like an "undo" and a "clear all" button, maybe a "save as" for a big projet who would take several mesuraments would be nice too.

Thaks for posting, you have some great ideas. I think you're right that a Ctrl-Z undo feature or button would be a good improvement.

The are a couple key combinations that I need to add to the help file. While you're adding a selection pressing 'Enter' will close the selection, pressing 'Esc' will clear the current shape, and right clicking will add the last point on a selection. I'll add in more detailed help soon.

The sheets are automatically saved so I'm not sure if we need a specific 'Save As' button.

I'm glad you have the Calipers and think this is useful too, there's a little overlap, and in future versions I'm going to allow automatic sharing of custom units that you define.