To edit a scanned document, please open the PDF in PhantomPDF and select Edit > Edit Object > Image. (There should be a small arrow under Edit Object that allows you to choose Image as a Sub Menu)
Once Edit Object > Image is selected, Double click on the center of the PDF. This will now enlarge the view along with new menu options on the menu bar.
To erase an area, you can use the eraser tool or rectangular marquee tool. (Shaded Square labeled Select underneath) Eraser tool can be selected and you are to scribble the area while clicking and holding. To use the Rectangular Marquee tool, please select The shaded Rectangle and create a box over the area and select the option Cutout. (Screenshot attached) This will now remove the selected area.
Once the area is removed, you are able to save and apply changes by selecting the Green Check labeled as Apply Changes. Now you are able to select Edit > Add Text and double click on the area you removed and start typing on your keyboard to add new text.