PDF Viewer

You can use the PdfViewer class to show a preview of PDF files in a ProcessWire files field:

Usage

The PdfViewer can be added to any field via hook:

wire()->addHookAfter(
  'Inputfield::render',
  function($event) {
    // only add viewer to a specific field
    $f = $event->object;
    if ($f->name !== 'your-field-name') return;

    // render iframes
    /** @var RockPdf $pdf */
    $pdf = wire()->modules->get('RockPdf');
    $pdf->getPdfViewer()
      ->field($f)
      ->height('600') // height in pixels

      // by default the viewer will use $file->url for the iframe src attribute
      // in case you have access-protected files you can provide a custom src:
      ->src('/rockinvoice/pdf/{id}/{basename}');

    // replace the original field markup with the pdf viewer
    $event->return = $viewer->render();
  }
);

Show a PDF in the browser

RockPdf offers a serve method that you can use to grab any PDF file and show it in the browser:

/** @var RockPdf $pdf */
$pdf = wire()->modules->get('RockPdf');
$pdf->serve($pagefile);

Note: The pagefile needs to be a standard ProcessWire Pagefile object, eg the return value of $page->getFormatted('mypdf.first').