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Try these:

Access the PDF in question, bypassing the CDN (e.g. directly from the Liferay server) and note the HTTP-Headers that are delivered. These might block the CDN from caching.

Check if the CDN has some explicit configuration options that might black- or white-list some of the URLs for either documents or previews. Especially in larger environments, we sometimes see one admin configuring "as far as they can observe", only for another one (e.g. you) to later figure out that this was not enough.

Also, check the configured host names: If the request for the preview bypasses the CDN because it uses a host name that is not handled by the CDN, you can either change that on the Liferay side, or also map that host name in the CDN. (Variations with and without "www" are good candidates, now that browsers effectively hide the actual host name they're requesting)

Hi, 

Thanks for the ideas.. here some pics:

Here headers from local lfieray portal:

Headers_Local

Here from the CDN:

Headers_CDN

And yes, they are world readable.

Thanks a lot for any clue...

Michael.

Hi Sergio

Currently, the pdfs are already being cached on the CDN... but when you hit download or preview the files,... they are always downloaded from the Liferay portal and not from the CDN. Please ask if anything else needs to be done for Liferay to send it to the CDN and not “provide it itself”.

Regards,

Hello Elena, did you apply the configuration I suggested?

Any changes?

Hi Sergio,

We apply the indicated configuration but the operation remains the same.

​​​​​​​

Any suggestions?

I set up the configuration to be public and TTL of 3600 seconds and when I request the file with its URL, I can see the expected headers.

Inspecting with Developer Tools, I can see

cache-control:public, max-age=3600