I know how to set content-disposition header for dynamic requests, but how to set it for static files.
Problem is that GAE java production version automatically sets to attachment content-disposition for static file requests (btw default local development content-disposition is inline), but I need to set it to inline.
Now when somebody tries to open static pdf file browser automatically starts download instead to try to open it in new tab.
Besides mime type and expiration, you don't have much control over how static files are served (see Google app.yaml documentation). If you need fine-grained control, you can store the PDF in the Datastore as a Blob and write a handler for it.
(Not to be confused with the Blobstore API)
All my pdf files are under /pdf/ path. I have created web request for /pdfi/ uri that with url fetch service fetches requested file under /pdf/ path and sets content-disposition to inline.
Now where ever (static html, etc.) there was link for any pdf file I have replaced /pdf/ with /pdfi/ and everything works. When and if GAE team allow us to set content-disposition for static files I will simply change every link from /pdfi/ to /pdf/
