title: JAVA Merge 2 PDF byte arrays
body: <p>I receive two PDFs, each as a byte array. So now I have 2 arrays, a[] and b[].
  I concatenate them and save them to c[].
  When I convert c[] to a PDF, only the 2nd file shows up. When I check the length of c[], it is len(a[]) + len(b[]).</p>
  <p>I found <a href="https://stackoverflow.com/questions/46288556/second-byte-overwrites-first-byte-while-merging-the-pdf">other questions</a> about this for different programming languages, and they say that I can't just concatenate them like this, we need to use a PDF authoring library. Since I receive byte arrays to begin with, is there anything else that could work in my situation?</p>