title: FPDF error: Unable to find "startxref" keyword
body: <p>I have an app that renders PDFs with <a href="http://www.fpdf.org/" rel="noreferrer">FPDF</a>.</p>
  
  <p>It was working fine and for some reasons I had to change the PDF files and now I get this error:</p>
  
  <p><code>Unable to find "startxref" keyword</code></p>
  
  <p><a href="https://i.stack.imgur.com/hTQ8s.png" rel="noreferrer"><img src="https://i.stack.imgur.com/hTQ8s.png" alt="enter image description here"></a></p>
  
  <p>If I restore the original files, the same error happens.</p>
  
  <p>How do I fix this error?</p>