Since pdftotext defaults to inserting form feed characters between pages, you can examine each line for a form feed character as an indication of pagination:

use strict;
use warnings;

my $i       = 0;
my $pageNum = 1;

open my $fh, "pdftotext -layout multipage.pdf - |" or die $!;
print "---------- Begin Page $pageNum ----------\n";

while ( my $line = <$fh> ) {
    if ( $line =~ /\xC/ ) {
        print "\n---------- End Page $pageNum ----------\n";
        $pageNum++;
        print "---------- Begin Page $pageNum ----------\n";
    }
    
    $i++;
    print "\n<div class=\"line\"><div>$i</div>$line</div>";
}

close $fh;
[download]

Another option which may serve you is using CAM::PDF:

use strict;
use warnings;
use CAM::PDF;

my $pdf = CAM::PDF->new('multipage.pdf');

for my $pageNumber ( 1 .. $pdf->numPages() ) {
    my $pageText = $pdf->getPageText($pageNumber);
    my @certainLines = ( split /\n/, $pageText )[ 9 .. 14 ];

    print "---------- Lines 10 - 15 on Page $pageNumber ----------\n";
    print +( join "\n", @certainLines ) . "\n";
    print "---------- End Page $pageNumber ----------\n";
}
[download]

The above shows how to grab a range of text lines from the converted pdf page. You may find, however, that pdftotext does a better rendering job.

Hope this helps!