Invisible Text: A PDF Superhero Power

A Datalogics customer that provides print services to global organizations recently came to us with an unusual request: They needed to be able to place information on a document that could either be copied and pasted or extracted as text – but that wouldn’t visually affect the appearance of the PDF itself - and they needed it to work well when they flattened transparencies.

In other words, they needed invisible text that would not affect the performance of their print workflows.

What makes “invisible text” useful in this situation is the associated font’s ToUnicode information, which allows the invisible text to be highlighted in any PDF viewer and copied and pasted into a different application.

Initially, the company tried to accomplish its goal with type3 fonts with blank glyphs. This is a special type of PDF font that is not based on an embedded or external font file; instead, each glyph is essentially a miniature PDF page. Unfortunately, flattening transparencies completely removed type3 fonts they thought would work (the type3 font glyph content streams were effectively being inserted directly into the page’s content streams).

Additionally, flattening the transparencies took time which could put them behind on their print schedule, and they could not pre-process or pre-RIP the documents due to the need to control the screening process.

With Datalogics’ introduction of the permitType3Fonts flattener option, Adobe PDF Library transparency flattener no longer removed type3 fonts unnecessarily. The Library also cleans up the ToUnicode table to ensure it does not contain extraneous information.

The result? The company was able to add this invisible text to the documents without compromising their rated print speeds, keeping their clients happy.

To learn more about Adobe PDF Library and see what it can do for your PDF workflows, visit our website and request a free trial.