Hello guys! I have this problem: I had put pdf in my new lesson and, when I try to look at it, I have this message: PDF: Please download and install pdf.js! But my sysadmin told me that was already done! Clearly, the pdf.js is not recognized here... Where I have to go in the setting to correct it? Thanks in advance for your help. Regards.
First you need to be sure that the pdf.js library is located in the correct place in your side.
For details regarding this please take a look at https://www.drupal.org/project/pdf under How to install pdf.js. Make sure there is no issue with the file/folders structure naming, such as uppercase/lowercase issues.
After that, just clear the site cache. If the library is in the correct place, it will display correctly.