GIMP is free image editing software that can open and edit various image format files including PDFs. Editing a PDF in GIMP is like editing a photo; you can easily add or remove objects from your file and export the file in the original or a variety of formats. Using selecting and blending tools from the GIMP Toolbox can help you crop an unwanted object out of a PDF file by covering the object with the background color while leaving the other parts of the file intact.
Open GIMP, click File and choose Open... from among the drop-down list.
Locate the PDF file you want to edit and click Open from the Open Image window.
Confirm the page of the PDF file you want to import to GIMP and click Import.
Choose the Rectangle Select Tool from the Toolbox and select the object you want to crop out of the PDF.
Choose the Blend Tool from the Toolbox.
Apply the Blend Tool to the selected area.
Right-click the blended area and choose Fill with BG Color under Edit from among the drop-down list to fill the area with the background color.
Check the result and confirm that the image has been edited out of the PDF document.
Go to File and click Export As... to save and export the edited PDF file. As an alternative, select the Export As... function by pressing Shift-Ctrl-E.
Name the file, navigate to where you want to save it and click Export from the Export Image window to save your work.