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Mastering PDF Generation with PDFreactor: Tips, Tools, and Insights

PDFreactor by RealObjects is an incredibly powerful engine for generating PDFs from HTML. It supports modern CSS, JavaScript, and goes beyond the capabilities of other libraries like jsPDF, Puppeteer, wkhtml, or pdfHTML. PDFreactor can generate PDFs at professional printing grade and create highly interactive PDFs, such as those containing forms and other interactive elements.

While its versatility makes it a top-tier choice for PDF generation, there are some nuances and best practices to keep in mind when working with it. Having built numerous complex templates using PDFreactor, I am excited to share my learnings, tips, and tricks in this article.


Documentation: Your Best Friend

One of the first things to note about PDFreactor is its excellent documentation. The official documentation is well-written, regularly updated, and indispensable for both beginners and seasoned developers.


Essential Tools for Building and Debugging

When working with PDFreactor, having the right tools can make the difference between frustration and seamless development. Here are three tools that are helpful when building and debugging PDF templates.

PDFreactor Inspector

Think of the PDFreactor Inspector as a web inspector for your PDF files. This tool allows you to debug the markup and CSS of generated PDF documents. By enabling the inspectableSettings option, you can explore the structure and styling of your PDF much like you would inspect a web page in a browser.

Fiddle for PDFreactor

PDFreactor’s Fiddle is basically a CodePen-like tool, but designed specifically for PDF templates. It allows you to:

PDF Inspector App

The PDF Inspector App is extremely useful for advanced diagnostics and deep dives into the generated PDF file. Unlike the PDFreactor Inspector, this tool analyzes the actual PDF document tree rather than the HTML markup it’s generated from. With the PDF Inspector App, you can explore the binary structure of the PDF and analyze various components like objects, fonts, images, and other resources within the file. This makes it invaluable for troubleshooting rendering issues by providing insight into how elements are structured in the final PDF document.

PDF Inspector App
PDF Inspector App is a tool for advanced diagnostics and deep dives into the generated PDF file.

Tips & Tricks for Effective Template Design

Avoid Cumulative Rasterized Elements

Embedding rasterized image assets repeatedly can drastically increase PDF file sizes, particularly in multi-page documents. Although PDFreactor employs an internal caching mechanism to enhance generation performance, it does not help with reducing the final file size.

(Ab)using PDF Comments to show content on mouse hover or click

PDF annotations can be leveraged to present additional information interactively, such as showing values for chart axis labels on hover, or displaying additional information on mouse hover of an icon. While this usage extends beyond traditional annotation purposes (which would be document review), it enables creative solutions for dynamic PDF functionality.

PDF comments can be (ab)used to show additional content on mouse hover or click.

During my experimentation with PDF comments, I discovered several challenges in achieving consistent visual representation across different PDF viewers. The idea was to use invisible rectangles or icons defined as comments, but this proved to be quite tricky to implement reliably.

After extensive testing, I found that using -ro-comment-style: underline provides the best results for nearly hiding the comment indicator while allowing custom icons to be displayed instead. This approach offers the most consistent and visually pleasing solution among the various options I explored.

.ro-comment{
  /* Propertary PDFreactor comment properties */
  -ro-comment-content: -ro-attr(text);
  -ro-comment-style: underline;
  -ro-comment-state: open;
  -ro-comment-title: -ro-attr(author);

  /* Size of the comment indicator */
  width: 18pt;
  height: 18pt;
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 9;

  /* Required to overwrite the default comment background color. */
  background-color: transparent !important; 
  /* Position of the comment indicator. */
  position: absolute;
  left: 242pt;
  top: 2pt;
}
<span class="ro-comment"
  text="This is the comment text. It does not support any special formatting, but line breaks are supported."
  style="-ro-comment-color: #F2F">

  <svg width="12" height="12" viewBox="0 0 12 12" fill="none" xmlns="http://www.w3.org/2000/svg">
    ...
  </svg>
</span>

However, it’s important to note that comment rendering varies significantly between PDF viewers:

PDF comments in different PDF viewers
Rendered output of the same -ro-comment in different PDF viewers, from left to right: Adobe Acrobat, Chrome, Apple Preview.

These inconsistencies across PDF viewers make it crucial to test your implementation thoroughly across different platforms if you plan to use this technique in production.


JavaScript Integration

The integration of JavaScript in PDF templates offers unique challenges due to the static nature of the generated PDFs. PDFreactor 12.0.0 significantly improved JavaScript support by switching from Rhino to GraalJS, which complies with ECMAScript 2024 standards (could not be said for Rhino).

Implementation Differences compared to web development

Library & Framework Support

Thanks for reading! If you'd like to share your thoughts you can leave a comment below, send me an email, or hit me up on Mastodon or Bluesky.