Adobe sdk customize file save location

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Developing a site using adobe sdk to enable annotations and other features on a pdf by using the mentioned link https://documentcloud.adobe.com/view-sdk-demo/index.html . But on clicking on save button the file is saved at default browser download location. I want to change the save location by programming I went through the documentation using link below https://www.adobe.com/devnet-docs/dcsdk_io/viewSDK/howtos_ui.html#save-a-pdf.  I am encountering issue at the following api level. Any suggestions are greatly appreciated.

adobeDCView.registerCallback(
  AdobeDC.View.Enum.CallbackType.SAVE_API,
  function(metaData, content, options) {...},
  {}
);

[Test Screen Name]

Web apps cannot directly write any file on the user's hard disk (with choice of location). That is fundamental and very important.

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I want to save the file on a server not on local hard disk