Correct some my descriptions (more detail)： Correct: PKCanvasViewDelegate inherits UIScrollViewDelegate, So it can conform all UIScrollViewDelegate's methods. However, I need to add PKCanvasView to another view(PDFView's documentView), so that can doodle on PDFDocument. I had already achieved it. But still when zooming PDFView, my PKCanvasView that as subview of PDFView's documentView was scaled too. Then the drawing was blurred. How to fix it?

Have you found solution? I meet the same trouble, I only know that the eraser's width changing following with touch.altitudeAngle values, so, I try to find some approach to set a fixed touch.altitudeAngle value when canvas's PKTool was PKEraserTool. But not success so far.