Hi @sweetu ve ,
According to my research and testing, unfortunately we cannot use SPFX to implement this feature, and we cannot manage download permissions for every file. Currently we can only use SharePoint access permissions. However, the read
permission also includes downloading documents, so there is currently no way to achieve the function of obtaining the approval of the administrator and otherwise it will not be possible to download. Thank you for your understanding.
More information for reference: User permissions and permission levels in SharePoint Server
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