Getting 403 on pdf files only

[shearer3000]

hi

We have a website set up in Azure and is configured with UmbracoFileSystemProviders.Azure for media. Image urls work fine (inc the Image processor handler aka CloudImageService) , but PDF urls return a 403. If i browse to the PDF file in the Storage Explorer it opens without issue.

I have configured the provider as per the docs, but is there anything i could have missed in regards to the StaticFileHandler, StaticFile handlers and pdfs?

NB the site is currently behind an IP whitelist (ipSecurity in web.config). I'm not sure why that would make a difference but need to mention it as the 403 seems to be coming from that level?

thanks
Andrew