Chrome Version: 66.0.3359.139 (Official Build) (64-bit)
OS: Linux, Mac OS X 10.13.4

What steps will reproduce the problem?
(1) Go to https://www.canada.ca/en/immigration-refugees-citizenship/services/application/application-forms-guides.html
(2) Select a form (e.g. 5257) in the drop down.
(3) Click "Get the form"
(4) Observe the PDF open with a message "Please wait... If this message is not eventually replaced by the proper contents of the document, your PDF viewer may not be able to display this type of document. You can upgrade to the latest version of Adobe Reader..."
(5) Wait.

What is the expected result?
The contents of the form is downloaded and shows up in the viewer.

What happens instead?
The contents doesn't get updated which according to the message means the viewer is not supporting whatever feature this PDF uses.

Alternatively, an option allowing me to open the URL in an external viewer (like Adobe Reader) would be nice. The Reader doesn't allow me to open a URL, only local files -- so I can't use it as a workaround alone. I had to open the form in Firefox and use its option to open the PDF in an external editor to get it to Adobe Reader and there the content downloaded properly.

Note that there're 250k people migrating to Canada a year (according to Google search) plus I expect way more temporary visitors who need a visa so it probably affects plenty of users overall.