[Gimp-user] PDF with multiple images-original scan from off-white paper

[FrGuidoSarducci <forums gimpusers com>]

I have a 250+ page PDF document.  Every page of this document contains an
image.  The original image that was scanned was on off-white paper.  I want to
print the PDF on white paper, but the off-white background of the original paper
stands out. I am unable to get the original images.
I was able to get rid of the off-white color thru GIMP (2.8.14) using
Select->By Color and then Bucket Fill.  I am new enough at GIMP that I don't
know if it's possible to make this change on all of the images at once.  Is this
possible?  if so, can someone point me in the right direction?  Thanks.

-- 
FrGuidoSarducci (via www.gimpusers.com/forums)