script que mostra como unir pdfs com pdftk

pdftk.php

<?php

require 'vendor/autoload.php';

use \mikehaertl\pdftk\Pdf;

$pdf = new Pdf;

$files = [
    'files/2484_27132950_1.pdf',
    'files/2486_28105431_1.pdf',
    'files/2509_21093914_1.pdf',
    'files/2509_21093914_1.pdf_cp.pdf',
    'files/2516_21095403_1.pdf',
    'files/285_21163310_1.pdf',
    'files/285_21163310_2.pdf',
    'files/285_21163310_3.pdf',
    'files/285_21163311_4.pdf',
    'files/285_21163311_5.pdf',
    'files/334_15133619_1.pdf',
    'files/334_15134509_1.pdf',
    'files/334_17110729_1.pdf',
    'files/334_17110730_2.pdf',
    'files/334_17161755_1.pdf',
    'files/334_17161803_1.pdf',
    'files/334_17161811_1.pdf',
    'files/334_17161819_1.pdf',
    'files/334_17162643_1.pdf',
    'files/334_17162811_1.pdf',
    'files/334_17162928_1.pdf',
    'files/334_17163338_1.pdf',
    'files/334_17163449_1.pdf',
    'files/334_17163556_1.pdf',
    'files/334_17163634_1.pdf',
    'files/334_17163736_1.pdf',
    'files/334_17163736_2.pdf',
    'files/334_17163737_3.pdf',
    'files/334_17163737_4.pdf',
    'files/334_17163737_5.pdf',
    'files/334_17163738_6.pdf',
    'files/334_17163738_7.pdf',
    'files/334_17163832_1.pdf',
    'files/334_17163833_2.pdf',
    'files/334_17163833_3.pdf',
    'files/334_17163834_4.pdf',
    'files/334_17163834_5.pdf',
    'files/334_17163834_6.pdf',
    'files/334_17163835_7.pdf',
    'files/334_17163835_8.pdf',
    'files/334_17163835_9.pdf',
    'files/334_17163836_10.pdf',
    'files/334_17163836_11.pdf',
    'files/334_17163836_12.pdf',
    'files/334_17163837_13.pdf',
    'files/334_17163837_14.pdf',
    'files/334_17163837_15.pdf',
    'files/334_17163837_16.pdf',
    'files/334_17163838_17.pdf',
    'files/334_17163838_18.pdf',
    'files/334_17163838_19.pdf',
    'files/334_17163839_20.pdf',
    'files/334_17163931_1.pdf',
    'files/334_17163931_2.pdf',
    'files/334_17163931_3.pdf',
    'files/334_17163932_4.pdf',
    'files/334_17163932_5.pdf',
    'files/334_17163932_6.pdf',
    'files/334_17163932_7.pdf',
    'files/334_17163933_10.pdf',
    'files/334_17163933_11.pdf',
    'files/334_17163933_8.pdf',
    'files/334_17163933_8.pdf_cp.pdf',
    'files/334_17163933_9.pdf',
    'files/334_17163933_9.pdf_cp.pdf',
    'files/334_17163934_12.pdf',
    'files/334_17163934_13.pdf',
    'files/334_17163934_14.pdf',
    'files/334_17164150_1.pdf',
    'files/334_17164150_2.pdf',
    'files/334_17164150_3.pdf',
    'files/334_17164151_4.pdf',
    'files/334_17164151_5.pdf',
    'files/334_17164151_5.pdf_cp.pdf',
    'files/334_17164151_6.pdf',
    'files/334_17164151_7.pdf',
    'files/334_17164151_8.pdf',
    'files/334_17164152_10.pdf',
    'files/334_17164152_9.pdf',
    'files/334_17164246_1.pdf',
    'files/334_17164246_2.pdf',
    'files/334_17164247_3.pdf',
    'files/334_17164247_4.pdf',
    'files/334_17164247_5.pdf',
    'files/334_17164247_6.pdf',
    'files/334_17164247_7.pdf',
    'files/334_17164248_10.pdf',
    'files/334_17164248_8.pdf',
    'files/334_17164248_9.pdf',
    'files/334_17164326_1.pdf',
    'files/334_17164326_2.pdf',
    'files/334_17164326_3.pdf',
    'files/334_17164327_4.pdf',
    'files/334_17164327_5.pdf',
    'files/334_17164327_6.pdf',
    'files/334_17164327_7.pdf',
    'files/334_17164328_10.pdf',
    'files/334_17164328_8.pdf',
    'files/334_17164328_9.pdf',
    'files/334_17164439_1.pdf',
    'files/334_17164439_2.pdf',
    'files/334_17164439_3.pdf',
    'files/334_17164532_1.pdf',
    'files/334_17164532_2.pdf',
    'files/334_17164532_3.pdf',
    'files/334_17164533_4.pdf',
    'files/334_17164533_5.pdf',
    'files/334_17164533_6.pdf',
    'files/334_17164533_7.pdf',
    'files/334_17164533_8.pdf',
    'files/334_17164533_9.pdf',
    'files/334_17164534_10.pdf',
    'files/334_17164534_11.pdf',
    'files/334_17164534_12.pdf',
    'files/334_17164735_1.pdf',
    'files/334_17164736_2.pdf',
    'files/334_17164736_3.pdf',
    'files/334_17164736_4.pdf',
    'files/334_17164736_5.pdf',
    'files/334_17164736_6.pdf',
    'files/334_17164737_10.pdf',
    'files/334_17164737_11.pdf',
    'files/334_17164737_12.pdf',
    'files/334_17164737_7.pdf',
    'files/334_17164737_8.pdf',
    'files/334_17164737_9.pdf',
    'files/334_17164738_13.pdf',
    'files/334_17164738_14.pdf',
    'files/334_17164738_15.pdf',
    'files/334_17164738_16.pdf',
    'files/334_17164738_17.pdf',
    'files/334_17164739_18.pdf',
    'files/334_17164739_19.pdf',
    'files/334_17164739_20.pdf',
    'files/334_17164849_1.pdf',
    'files/334_17164849_2.pdf',
    'files/334_17164849_3.pdf',
    'files/334_17164849_4.pdf',
    'files/334_17164850_5.pdf',
    'files/334_17164850_6.pdf',
    'files/334_17164850_7.pdf',
    'files/334_17164850_8.pdf',
    'files/334_17164937_1.pdf',
    'files/334_17164937_2.pdf',
    'files/334_17164938_3.pdf',
    'files/334_17164938_4.pdf',
    'files/334_17164938_5.pdf',
    'files/334_17164939_6.pdf',
    'files/334_17164939_7.pdf',
    'files/334_17164939_8.pdf',
    'files/334_18121256_1.pdf',
    'files/334_18121256_1.pdf_cp.pdf',
    'files/334_18130158_1.pdf',
    'files/334_18130158_2.pdf',
    'files/334_18130158_3.pdf',
    'files/334_18130159_4.pdf',
    'files/334_18130159_5.pdf',
    'files/334_18130159_6.pdf',
    'files/334_18130159_7.pdf',
    'files/334_18130159_8.pdf',
    'files/334_18130159_9.pdf',
    'files/334_18130224_1.pdf',
    'files/334_18130224_2.pdf',
    'files/334_18130225_3.pdf',
    'files/334_18130225_4.pdf',
    'files/334_18130225_5.pdf',
    'files/334_18130225_6.pdf',
    'files/334_18130252_1.pdf',
    'files/334_18130317_1.pdf',
    'files/334_18130318_2.pdf',
    'files/334_18133011_1.pdf',
    'files/334_18133011_1.pdf_cp.pdf',
    'files/334_18140319_1.pdf',
    'files/334_18141854_1.pdf',
    'files/337_18150710_1.pdf',
    'files/338_21102536_1.pdf',
    'files/339_21134912_1.pdf',
    'files/339_21134913_2.pdf',
    'files/386_13_138_02162417.pdf',
    'files/386_13_138_02163142.pdf',
    'files/386_13_138_02171626.pdf',
    'files/386_13_138_02182007.pdf',
    'files/386_13_138_02213850.pdf',
    'files/386_13_139_12170342.pdf',
    'files/386_13_139_12170535.pdf',
    'files/386_13_143_02180545.pdf',
    'files/386_13_145_02154416.pdf',
    'files/386_13_145_12170544.pdf',
    'files/386_13_145_12170647.pdf',
    'files/386_13_151_02212032.pdf',
    'files/386_13_178_02212503.pdf',
    'files/386_13_217_02183942.pdf',
    'files/386_13_217_02210017.pdf',
    'files/386_13_217_02215740.pdf',
    'files/386_13_2481_01122449.pdf',
    'files/386_13_2495_02180259.pdf',
    'files/386_13_2947_02184116.pdf',
    'files/620_18143356_1.pdf',
    'files/620_18143806_1.pdf',
    'files/620_18143807_2.pdf',
    'files/620_18143807_3.pdf',
    'files/620_18143807_4.pdf',
    'files/620_18143807_5.pdf',
    'files/620_18143807_6.pdf',
    'files/673_18144200_1.pdf',
    'files/673_18144200_1.pdf_cp.pdf',
    'files/673_18144200_2.pdf',
    'files/673_18144201_3.pdf',
    'files/aceites_386.pdf',
    'files/assinas_386.pdf',
    'files/capa_386.pdf',
    'files/doc_123_386.pdf',
    'files/doc_22_386_1.pdf',
    'files/doc_24_386_2.pdf',
    'files/doc_24_386.pdf',
    'files/doc_26_386.pdf',
    'files/doc_36_386_2.pdf',
    'files/doc_36_386_3.pdf',
    'files/doc_36_386.pdf',
    'files/doc_53_386_1.pdf',
    'files/doc_54_386_1.pdf',
    'files/doc_54_386_2.pdf',
    'files/doc_54_386_3.pdf',
    'files/doc_55_386_1.pdf',
    'files/doc_55_386_2.pdf',
    'files/doc_56_386_1.pdf',
    'files/doc_56_386_2.pdf',
    'files/doc_56_386_3.pdf',
    'files/doc_57_386.pdf',
    'files/doc_58_386.pdf',
    'files/doc_59_386.pdf',
    'files/doc_60_386_3.pdf',
    'files/doc_60_386_4.pdf',
    'files/doc_60_386.pdf',
    'files/doc_61_386_1.pdf',
    'files/proc_386.pdf',
    'files/processo_386.pdf',
    ];

echo "iniciando a união de arquivos\n";

try {

    foreach($files as $file){
        echo "{$file}\n";
        $pdf->addFile($file);
    }

    echo "salvando... \n";
    echo "{$pdf->getTmpFile()}\n";
    $saved = $pdf->saveAs('files/pdftk.pdf');

    if(!$saved){
        echo "{$pdf->getError()}\n";
        return 1;
    }

    echo "Pdf gerado com sucesso\n";
    return 0;


} catch (\Exception $e) {
    echo $e->getMessage();
}