How can I “white-out” marks on poor/unclean scans or handwritten marks on my document?

The method to delete marks on a PDF depends on how the image is implemented on the document. There are two types of images on a PDF document: vector graphics, and bitmap images.

Vector graphics are images embedded into the document like a watermark. If the image is a vector graphic, you cannot select and edit it as you would a bitmap image. If something is implemented on your PDF as a vector graphic, there are a couple ways to "white out" marks or images on a PDF. 

One approach is to use the Select Rectangle Tool to select the area of the page you want to "white out" and choose Format > Redact Text-Erase or Redact Text-Block (you can adjust the block color in Object Properties) to erase/ cover over the image.

If that does not work for your purposes, another approach is to use a solid rectangle (Rectangle Tool) or text box (Text Tool) to create a white out effect:

1. Create a rectangle over the text or image using the Rectangle Tool or Text Tool (the Text Tool is helpful if you want to simultaneously cover over and include new text).

2. Then, in the Editing bar > Object Properties > Object Color, choose solid background fill for the shape. Choose a a color from the color palette.

Bitmap images are selectable and editable on a PDF. To determine if your image is selectable, choose Arrange > Unlock All and use the Edit tool to select the image. If you can select the image and resize it or move it around, his means, once the image is select, you can tap "delete" and the image will disappear from the document.