How to turn pdf from Grayscale to pure white

[Guest]

I have an invoice which originally was color, I used Preflight to turn it into Grayscale, however, the gray was still too dark. Now, I need to turn it into white background. I found out under "output preview", if I select "Text" in the show field, that works for me. How can I save it? Thanks,

[Willi Adelberger]

As long as we don't know the kind of PDF—where it was done, does it contain text or is it a scan, etc.—no reliable answer can be given.