I'm not entirely sure I understand what your problem is, but here is some code I use to make a "Test"-copy of a given PDF:
sub PrintTextAngle {
    my ($texthandler, $x, $y, $rot, $text, $options) = @_;
    $texthandler->transform('-translate'=> [6/mm+$x/mm,10/mm+$y/mm], '
+-rotate'=>$rot);
    $texthandler->text($text, $options);
}

my $pdf_input = PDF::API2->open("$Filename");
foreach my $pagenr (1..$pdf_input->pages) {
    my $page = $pdf_input->openpage($pagenr);
    my $texthandler = $page->text;
    my $font = $pdf_input->corefont( 'Helvetica-Bold',    -encode => '
+latin1' );
    $texthandler->fillcolor('grey');
    $texthandler->font($font, 256/pt);
    PrintTextAngle($texthandler, 50, 60, 45, "TEST");
    $texthandler->font($font, 56/pt);
    PrintTextAngle($texthandler, 20, 10, 0, "Do not throw away!");
}
$pdf_input->saveas("$Filename-TEST.pdf");

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This leaves the background (the imported PDF contents) intact and prints the text over this background (Though not semi-transparent, which you might want).

If you still insist on toying with the overprint setting, use this: 

my $EGOverprint = $pdf->egstate();
my $EGNormal = $pdf->egstate();
$EGOverprint->strokeoverprint(1);
$EGNormal->strokeoverprint(0);

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Before calling PrintTextAngle, set the Extended Graphics State using: 
$text->egstate($EGOverprint);

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Then print, and afterwards (if you want to print some more without using overprint) restore the Extended Graphics State with: 
$text->egstate($EGNormal);

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In reply to Re^3: PDF::API2 and opacity by Neighbour
in thread PDF::API2 and opacity by Anonymous Monk

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