WPViewPDF V4 PLUS has the ablity to load one PDF and use selected pages as watermarks for another PDF file.
Code
i := WPViewPDF1.CommandStrEx( COMPDF_LoadFileAsWatermark, OpenDialog1.FileName, StrToInt(edSourcePage.Text)-1);
if i<=0 then
ShowMessage('The PDF file cannot be loaded as watermark - Code=' + IntToStr(i))
else
begin
if rbOddPages.Checked then
i := WPViewPDF1.CommandStrEx( COMPDF_ApplyWatermark, 'odd', i)
else if rbEvenPages.Checked then
i := WPViewPDF1.CommandStrEx( COMPDF_ApplyWatermark, 'even', i)
else i := WPViewPDF1.CommandStrEx( COMPDF_ApplyWatermark, edPageRange.Text, i);
if i<=0 then
ShowMessage('The PDF page cannot be applied as watermark');
end;