Hi Shatal,
Thank you for contacting WebViewer Support.
Our Polyline tool in the Shapes ToolGroup is able to produce multiple lines starting from the end of last clicked position.
If you would like to customize keys, here is the hotkey API available under UI instance:
https://www.pdftron.com/api/web/UI.Hotkeys.html#key
Best Regards,
Kevin Kim
Web Development Support Engineer
PDFTron Systems, Inc.
www.pdftron.com