When creating or opening a new document with the item 'New' or 'Open' from the File menu, pasting has no result. In the File menu, the options Copy and Paste are greyed out.
When opening a document or creating a new one, the Acrobat Selection Tool is activated. This means that PitStop is deactivated, which causes the Copy/Paste functions to be disabled.
Select the PitStop Selection Tool and click on the page. This will activate PitStop and the Copy/Paste functions.