Thanks,
Kalaivannan, that's just perfect. I my hands it looks like this:
private void AdjustMargins( SfRichTextBoxAdv richTextBoxAdv ) {
if ( richTextBoxAdv.Document is null ) return;
if ( !richTextBoxAdv.Document.Sections.Any() ) return;
for ( int i = 0; i < richTextBoxAdv.Document.Sections.Count; i++ ) {
SectionAdv section = richTextBoxAdv.Document.Sections[i];
section.SectionFormat.PageMargin = new Thickness( 0, 0, richTextBoxAdv.Width / 10, 0 );
}
}