I have a direct link to a PDF on my multi-lang Joomla 3.0 site. However, when browsing to the link, Joomla keeps on injecting the language code /en/
into the URL, thus resulting in a 404 error.
How should I link to this PDF so people can view it?
That's a bit strange, I guess it should be related to how you have linked the pdf. From where you link the pdf?
In any case a direct hard-coded link to the pdf file like:
images/sample.pdf
should work.
If this is how you have linked it, then you should give more details about your configuration, but also consider to check if you have any special redirections or SEF extensions.
Not sure of your configuration for multi-language but I suspect the /en/ is coming from the language plugin config. As a workaround, you could create a new "hidden" menu item for an external location and point it to the PDF file.
Depending on your editor you could then create the link in your content easily.
This is obviously not scalable for many PDFs.
This may be what @Ffrewin is suggesting(having re-read his answer).