Like a lot of Alfresco users, I spend a lot of time dealing with PDF documents.  Invoices, purchase orders, product specifications, documentation and signed authorizations all flow through our Alfresco system as PDFs.  Recently I had a need to watermark a subset of these documents, marking them as "official" or "draft" releases.  A bit of poking around revealed that there wasn't an open-source, free way to apply simple watermarks to PDF documents in Alfresco.  Generis has a solution, but it is a commercial package and provides a lot more functionality than I really need.  So, what to do?  Extend Alfresco, of course!

Alfresco allows developers to create custom actions that can manipulate nodes in the repository.  These actions can then be triggered via a content rule, perfect for my needs.  It's pretty simple:  a document is added to a space, the content rule is triggered and calls an action that can modify the new document.  While I was looking around for PDF tools for Alfresco, I came across Jared Ottley's blog, and specifically his Alfresco PDF Toolkit project.  I love to learn by example, and Jared's code was a nice, concise introduction to how custom actions work.  With a few days of coding, I was able to add a PDF watermarking action to his existing project.  The code has been added to the alfresco-pdf-toolkit project on Google Code.  It supports the following features:

• Selection of a watermark image and marked PDF destination
• Choice of watermark location:  top left, top right, bottom left, bottom right or centered
• Choice of watermark pages:  first, last, even, odd or all
• Choice of watermark depth:  above or below the PDF content.

You can either build the package from source or download the AMP file here.  For those that don't know, AMPs are one of the ways that extensions to Alfresco can be packaged.  AMPs are deployed using the Alfresco Module Management Tool.  Once you have installed the AMP and restarted Alfresco, you will find a few new actions available.  To try out the watermarking action, start by creating a space for inbound PDF documents and create a new content rule for the space.  Since this action will only work with PDF documents, set the condition to "Content of mimetype", as shown below: 

Select "Adobe PDF Document" from the mimetype list to ensure that this rule is only triggered when a PDF is added.

After you have set the mimetype and clicked "Next", select the "Watermark PDF" action from the list.  Click "Set Values and Add" to configure the PDF watermarking action:

The PDF Watermark action requries 5 parameters.  The first, the watermark image, is the image that you wish to have applied to your PDF.  Most common image formats are supported.  The second parameter is the destination.  This is the space into which the watermarked PDF will be placed.  The watermarked PDF will have the same name as the original, so it probably isn't a good idea to put it back into the same space.  Finally, you can select the pages to watermark, the position of the watermark, and whether the mark will be applied above or below the existing PDF content (similar to a CSS z-index).

Once the parameters are set, click OK to save.  Finish up the "Add Content Rule" wizard and you are all set.  Any PDF documents put into the space will now be watermarked and copied to the destination space you specified.

Additional feature requests are welcome, enjoy!