hi guys!
are there any pdf readers which can set the documents'background colour,even though the document maked from scanner?

Hi there,

unlike HTML, PDF is a document format that tries to convey as exactly a reproduction of the original as possible. So if the PDF document does specify a background color or pattern, PDF readers are supposed to display that. Only if the document doesn't specify a background, PDF readers are free to choose a color of their own, usually white.

So you have to intervene during creation of the PDF document. But on the other hand, a scanned document always has its own background, usually white or some kind of dirty white. And that'll be displayed as good as possible by a PDF viewer.

[X] Doc CPU

you can import it into Libreoffice
and set that background
an example
the COUNTER script for telemarketers