How to download a file from a SharePoint though a web site button?

I have a web page that has a button and a SharePoint library.

Once the user clicks the download button, the document will be downloaded from SharePoint with a watermark of the user trying to download this file.

Additionally, I need to manage who can access or download the file.

Therefore, the main points to consider are:

• User authentication to the SharePoint document library

• Pulling the document from the website itself

• Watermark feature

Thus, what is the most effective practice to achieve that and what should I use?

oh man, this is really an open and not quite detailed question 😟. Could you provide more context? what language are you using? have you already tried something and what is failing?

For now, the only help I may provide you is just general info 🙂:

User authentication to the SharePoint document library

if you are extending SharePoint or M365 with a SPFx solution you do not need to worry on auth. If it is totally aside I would recommend checking

• https://learn.microsoft.com/en-us/graph/auth/auth-concepts
• I would strongly recommend checking microsoft-graph-toolkit there is a mgt-login component

https://learn.microsoft.com/en-us/graph/toolkit/components/login

again here I would also recommend using MS Graph and endpoint like https://graph.microsoft.com/(version)/sites/(site-id)/drive/(drive-id)/items/(item-id)/content

• I guess this is a very similar topic: Sharepoint Graph API download file from Document library that are not listed as drive ("Site Pages" and others)

Watermark feature

as for this I would take a look at Microsoft 365 sensitivity labels feature and read more about it here

• https://learn.microsoft.com/en-us/microsoft-365/compliance/sensitivity-labels?view=o365-worldwide#what-sensitivity-labels-can-do

I hope this will be of any help. For sure it is a good start 🙂