# PDF Server 1.x-3.x to 5.x

### PDF Server 1.x-3.x to 5.x&#x20;

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**5.x PDF Serve**r requires an upgrade to **API Server 8.0.0** or higher.
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If you are using PDF Server APIs directly you need to change the way your application authorizes the requests:

* If you are doing client-to-server requests (your application is working on browser) then you should send requests to API Server's `/pdf-proxy` endpoint using `x-jwt-token` header, see [**PDF API section**](https://apidocs.form.io/#864ccc88-4585-053e-4302-c839d987271a) of API docs.
* If you are doing server-to-server requests (your application is working on the server and request readers cannot be exposed) then you can send requests directly to PDF Server using admin key authorization. To do this you should add the `FORMIO_PDF_ADMINKEY` environment variable to your PDF Server run config. Set it to some secret key. After that, you can authorize your requests using `x-admin-key` header, which should be the same as the environment variable value. See [**PDF Server direct API section**](https://apidocs.form.io/#8e817291-38df-4338-889f-14cf38de5fbd) of API docs.
