StepOnce you open the document, click on the “Insert” button and choose a needed tool to draw PDF online. Draw Free-Form Curved Lines in PDF. Use the Pencil Tool to Draw Lines on PDF. In UPDF you can draw both straight lines and free-form curved lines, depending on your How to Draw Lines on PDF. Here is a step-by-step instruction on drawing quick lines on PDF documents using PDFLiner: Upload your PDF – you can upload your ready-made ,  · By following these simple steps and utilizing the drawin