Error: There was a problem reading this document (18)? Answered

• Delete the PDF file from the computer. You can
  either delete it by using the Delete key, and then empty
  the Recycle Bin or delete it permanently by selecting the
  file and then pressing the Shift + Delete Now, you need
  to download the file again from its original source. Wait until Acrobat
  downloads the file completely. Try opening the PDF file once it is
  downloaded.
  
• Uninstall the Adobe Acrobat for
  this, open the Start menu and click on the icon for Control
  Panel. Once the Control Panel window opens,
  locate the Adobe Acrobat program from the list of
  installed programs and click on Uninstall. Follow the
  prompts that appear in the next window. Wait until the program is
  completely removed from the computer.
  
• Restart your computer now. Open the Start menu
  and then select the Restart button that you see among the
  power options. Once the computer reboots, go to the adobe.com website,
  navigate to the Downloads page, and locate the link for
  downloading the latest version of Adobe Acrobat
  Reader. Save the installation file in a preferred location and
  run it. Follow the prompts in the installation wizard to complete the
  setup.
  
• Open the same web page from where you got the
  corrupted PDF file. Download the file and make sure that it completes the
  process completely. Try opening the PDF file. It should work now; if not,
  proceed to the next step.
  
• Download a PDF Recovery program from any reputed
  site. Install it after downloading the setup file and follow the prompts
  shown. Run the program and proceed as instructed to repair the corrupt PDF
  file.
  
• In case you can't recover .pdf file via the
  recomendation, make use https://pdf.recoverytoolbox.com/ Recovery
  Toolbox for PDF

Try to update your pdf reader version to its latest

Broken PDF