Chrome's built-in PDF viewer won't display our PDF forms

Basically, you need to force the download of the PDF file.

If you edit the .htaccess file and add this code, all PDF files should be downloaded instead of opened in your site.

<FilesMatch "\.(?i:pdf)$">
  ForceType application/octet-stream
  Header set Content-Disposition attachment
</FilesMatch>

If that's not an option, add a message explaining the user to use "Right click > Save As" in the download link; notice that many sites do this, even sites from HP or Intel, so it's a common practice.

I have this same problem with one specific PDF form made with LiveCycle Designer, while other PDF forms made with the same tool were working. And I've just found the cause and the solution: the troublesome PDF form was made and saved as an "Adobe XML Dynamic form". I've just had to Save as... "Static Adobe PDF Form" and it now is displayed in every modern browser (Firefox 56, Chrome 62, Edge). Firefox does not yet implement filling of PDF forms, but it is displayed with its visual appearance; the other browsers allow filling it, except for the Digital signature box.

Before, all browsers displayed an English message saying something like Please wait.. If this content is not eventually replaced with the actual PDF contents, your viewer may not be able to properly display this PDF content.

Note, however, that if your workflow involves prefilling the form in server side before sending it to the user (for instance, if your website authenticates the user and uses its profile in your database to automatically fill his name, address, email, etc. in the form before sending it to him), you may need to stick to XML Dynamic forms and, therefore, the PDF must be opened with Adobe Reader or a similar application able to deal with XML Dynamic forms.