What software are you using to print your PDF files? If you are using the Chrome or Firefox browser, it is possible (and if you've not changed anything actually very likely) that you are not using Adobe's PDF viewer, but the built-in PDF viewer that they have embedded. If that's what you are dealing with, you need to get in touch with customer support for your browser.
Take a look at these pages, they contain Adobe's troubleshooting tips for problems with PDFs in the browser:
https://helpx.adobe.com/acrobat/kb/cant-view-pdf-web.html
https://helpx.adobe.com/acrobat/kb/pdf-browser-plugin-configuration.html
The 2nd link does explain how you can turn the PDF viewer on in your browser. However, Chrome decided not to support the plug-in interface that (among others) Adobe Reader/Acrobat uses, and you will not be able to use the instructions on that page to enable Reader on Chrome anymore (the page does say that Acrobat/Reader DC and Chrome is no longer a supported configuration).
If you are already using Adobe Reader or Acrobat, then take a look at this page:
Missing or Garbled Text Printing from IE9 to Adobe PDF Printer