Properly redacting PDF files can be an expensive job. Oftentimes, files are released with the impression that they are redacted because you can't see the redacted text. In reality, those big black rectangles can be removed quite easily with the right editor, leaving behind the confidential text that should have been removed.
Preseving PDF form content can be a concern as well. How can we be assured that form content is not altered after we receive it?
When a PDF is flattened, the layered content, like those floating black rectangles and form fields, are all combined into a single image layer.
There are many high cost solutions to achieve this. It can also be done with freely available PDF libraries. This solution uses Apache PDFBox, which is available under the Apache License. This project is licensed under the same license.
This project, along with all the libraries it uses are licensed under the Apache License.
For convenience, these binaries are bundled into the main build.
- PDFBox requires at least Java 8 to run. This project is compiled to work with Java 8 or better.
- Memory. Depending on the size of your PDF, it may take over 1 GB of memory to process it.
How to Redact in Adobe Acrobat Reader for Free
Check the Releases for an executable JAR file. Note that the executable JAR makes use of Java's JFileChooser class, so a GUI is required.
Alternatively, you can include the JAR file in your project, and call the static flattenPDF(File src, File dest) method.