Google Chrome comes with built-in PDF Viewer- aka Chrome PDF Viewer enabled by default, and PDFs you come across on a website through links or email attachments will be automatically opened and displayed by it to the user.
Make Chrome to always open PDFs in System Viewer, instead of the Chrome PDF Viewer
What if you’re using PDF Reader application like Adobe Reader or Foxit Reader on your computer and always want PDFs accessed in Chrome browser to open with it? For that, first you need to visit about:plugins and disable Chrome PDF Viewer (click on two disable buttons: one is for extension and other one is for the internal PDF Viewer), after that, try to download a PDF from any website in Google browser, when it reaches the downloads bar, click on the down arrow and select ‘Always open with System Viewer’.
So next time, when you download a PDF file in Chrome, it will be automatically open in default desktop PDF Reader installed on your system when the file download was complete.
You need to follow the same procedure and uncheck the option, after that, enable the built-in PDF Viewer for it to open and display PDFs in the browser.