To set up a PDF file as a page so you can click on the link to directly open the PDF file, please follow below steps to do so: 
  1. On your navigation bar, click Media drop-down and select Documents 
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  • Note: If you cannot see "Media", you may go to Settings > Menus & Pages and move the Media option from the right panel "Available Menu Options" to the left panel "Current Menu"
  1. Click Add Document + button to upload your desired PDF file into the system
  2. After the file is uploaded, right-click on the document and select Copy link address
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  1. Go to Settings > Menus & Pages, click New Link + button in right panel 
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  1. Enter Link name, and Link URL which is the link you just got from above step #3, click Save
  2. Move the newly created Link from the right panel to the left panel, drag and drop it to the desired position, click Save Menu button
After above is done, please refresh your website and you will see the link appears on your navigation bar, clicking on it will directly open the PDF file you uploaded.