Servlet Filter for PDF

Good Afternoon

I've been trying to setup a filter to check the property of a pdf and then do something based on that property. My only trouble is that the filter runs even if I set the extension to pdf. How would I go about setting the filter to only execute on requests with the pdf extension.

Here is how I am currently setting it:

@Component(service = Filter.class, 
property = { "sling.filter.scope=REQUEST",
"service.ranking=-700",
"sling.filter.extensions=pdf",
"sling.filter.methods=GET",
"sling.filter.methods=HEAD"})

Thanks!