PDF Ink Lite – Stamp PDFs with Customer Data

 
Oh, thanks for thinking of the countless volunteers who develop plugins for you to enjoy!

In the PDF Ink Lite “Housekeeping” settings, you can check the “Attribution” box. This will add a super tiny, invisible watermark to page 2 of your PDF files, linking back to PDF Ink. The attribution mark is almost impossible to spot — try it!

 
You can find the PDF Ink settings page by clicking on the “Settings for XXX” link under the PDF Ink Lite plugin title on your WordPress plugins panel.

 
Troubleshooting Steps

In order of simplest/obvious to more difficult/less obvious…
 

1. Is WooCommerce or Download Monitor or Easy Digital Downloads installed, and do you have a purchasable PDF product in your shop to watermark?
2. Have you checked the PDF Ink Lite settings checkbox to enable watermarking?
3. Have you entered your PDF file names correctly in the second field if you’ve entered any at all? This field is case-sensitive.
4. Make sure your PDF product downloads work without PDF Ink Lite activated, to narrow the problem.
5. Try watermarking a different PDF (one you didn’t create) to see if that PDF works. If your PDF has goofy syntax (and many do because good PDF syntax is “optional”), this plugin will not be able to read it. Use PDF Ink with SetaPDF-Stamper instead.
6. Is your PDF version 2.0? You’ll want to downgrade your PDF or use PDF Ink with SetaPDF-Stamper instead.
7. Choose a different font in the settings.
8. Update WordPress, and all plugins including this plugin to the most recent versions.
9. If your PHP version is the newest, try downgrading.
10. Is your Y fine-tuning adjustment moving the mark off the page? Read more below under “Why does the watermark go off the page, create blank pages?”.
11. Increase your PHP time limit and memory limits if they are set low (but don’t set too high, either). Server limitations can stop this plugin from functioning well.
12. If using WooCommerce, go to WooCommerce -> Settings -> PDF Ink Lite -> Logging and turn logging on. If using Easy Digital Downloads, go to Settings -> Misc -> Debug Mode and turn on logs. Run the program again, then look at the logs (EDD logs are under the Tools tab).
13. Check your WP debug logs. If logs suggest your PDF is “malformed” or “template does not exist,” try using Apple Preview application to resave your PDF by clicking “Export as PDF” in the menu. Preview might fix bad PDF syntax and allow your PDF to be processed for watermarking.

 
Please – definitely – get in touch with your issues via the WordPress.org support forum before leaving negative feedback about this free plugin.

To request help using the WordPress.org support forum, start here.

Do not use the WordPress.org support forum for help with the full (paid) version of PDF Ink – that is against WordPress.org rules. Conversely, use the WordPress.org support channel — not email — for PDF Ink Lite (free).

 
Try selecting the “Deja Vu,” “Furat,” or “M Sung” font in the plugin settings panel.

One reason watermarks might not show up is because the watermark contains special characters but you’re using a font which doesn’t support those characters. If none of the included fonts are subsetted for your language characters, you will need to programmatically add fonts yourself or look into purchasing the full version of this plugin, which has many more built-in fonts and supports font uploads.

 
Maybe set your PDF to $0 (free) and “Privately Published” (for WooCommerce). Or maybe create a coupon in your shop to allow 100% free purchases. Don’t share this coupon code with anyone! Test your watermark by purchasing PDFs from your shop using the coupon. It’s a bit more tedious. If you want easier on-the-fly testing, purchase the full version of this plugin.

 
Your watermark text string is too big or long for the page, and goes off it! Try decreasing font size or using the Y fine tuners to move the watermark back onto the page. Try lowering your “y-axis” value. This number corresponds to how many millimeters you want the watermark moved down the page. For example, if your PDF page is 11 inches tall, your Y-axis setting should be a deal less than 279.4mm in order for a watermark to show. The built-in adjustments on the settings page ultimately allow for watermarking on all document sizes. You may need to edit your watermark if it is too verbose.

You can use a negative integer value for your Y-tuner and measure up from the bottom of the page. This is especially helpful if your PDF has variable sized pages.

 
They are generated with a unique name and stored in the same folder as your original WordPress/Woo product media upload (usually wp-content/uploads/year/month/file). The unique name includes the order number and a time stamp. If your end user complains of not being able to access their custom PDF for some reason (most often after their max number of downloads is exceeded), you can find it in that folder, right alongside your original.

If you are using Woo FORCED downloads, the plugin attempts to delete the watermarked files after being delivered. This isn’t 100% reliable since it works on PHP shutdown. If you don’t like attempted deletion, you can change it with the ‘wwpdf_do_cleanup’ filter hook (set it to FALSE). The paid version of this plugin has improved file handling/removal.

 
PDF Ink is intended to watermark PDF (.pdf) files. If you are specifically looking to watermark image files (.jpg, .jpeg, .gif, .png, .etc), you may want to look into a plugin such as Image Watermark.

 
This plugin is just for PDF files, but the upgrade also works with EPUB files, and MOBI coverage is roadmapped.

 
PDF Ink Lite bridges your e-commerce PDFs and the open-source PDF reading library TCPDI and PDF writing TCPDF library. PDF Ink Lite functions by parsing/reading your PDF into memory the best it can, then adding a watermark to the PDF syntax and outputting a revised file. Between the reading and output, certain features may be lost and other features (interactive PDF elements like internal links and fillable forms) will be lost. This is a limitation of the open-source third-party libraries used (TCPDI/TCPDF) AND the wild-west nature of PDF syntax. It is not the fault of PDF Ink Lite, which simply connects your e-commerce to PDF manipulation libraries.

Ultimately, PDF Ink Lite is best for simple, smaller-sized and well-formed PDFs. If you are serious about watermarking and/or encrypting complex PDF files, purchase PDF Ink. It includes other libraries you can try free, and also allows you to link purchased 3rd party (non-GPL) libraries (such as SetaPDF Stamper) which work on any PDF. You might even find that the free libraries (TCPDI/TCPDF) included with PDF Ink (paid) work better than here in the free version! 😉

 
Yes, you can serve the file untouched if watermarking fails, and avoid any error messages, by using the following filter code in your (child) theme functions.php file:

add_filter( 'wwpdf_serve_unwatermarked_file', '__return_true' );

If you do not know how to edit your functions.php file, you can use the Code Snippets plugin to easily add this code to your WP site frontend.