 <p>As you give no code it's hard to suggest actual code... However, the customary way to make text invisible is to use the text render mode. All text in PDF has such a text render mode and it determines whether the text is rendered as filled text (normal), stroked text, filled and stroked... And one of the possibilities is "invisible" which makes sure the text isn't shown.</p> <p>When parsing text on a page iText amongst other things allows you to filter the text that is returned - see the FilteredRenderListener for example. During filtering you can then determine whether you're interested in the text or not. There is a lot of information about the text you can inspect using the TextRenderInfo object. This object has a method called "getTextRenderMode" that will return the above text render mode. If that call returns "3", you know the text is rendered invisibly.</p> <p>Now, if you want to know for sure whether this text is indeed rendered invisibly (and not using one of the other nasty tricks @jongware suggests in his comment, you'll have to inspect the PDF or share an example with us so that we can take a look.</p>