Not a real answer to your question. As a workaround you could consider combining all pdf documents in a zip file. You can do this using an appstore widget (search for zip), so no need to create a java program yourself.
Have a look at apache pdfbox for merging pdf files.
I added a function to CommunityCommons to overlay PDFs. It uses pdfbox. If you download the most recent CommunityCommons version for Mx5 you already get the Java jars necessary for this. Then you can create your own Java action to do this. If you make it generic enough, it would make a nice addition to the overlay function.
With the above solution, Merge PDF Tool you can merge PDF documents but there are some limitations of using online utility one among them is file number limitation i.e. at a time a user can merge few PDF documents. The above-described utility can merge only 5 PDF documents at a time. Therefore, to overcome such limitation there is a need for some alternate solution. In such cases, it is suggested to use professional utility with Combine Multiple PDF File With this software, a user can merge multiple PDF documents without any file size and number limitation.
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