Allow an external user to upload files
This is how you allow an external user to upload a file without giving them access to your Synology NAS.
Open File Station.
Navigate to where you would like the file uploaded.
Click Action in the top menu > Create upload file request.
Fill out the information and copy the link. Send the link to the person you would like to upload the file.
Here is the knowledge base article on the Synology website:
https://www.synology.com/en-us/knowledgebase/DSM/help/FileStation/file_request