You can force files (such as PDFs or JPEGs) to display directly in the browser rather than being downloaded.
If you have a link to an image or a file that you want to open within the browser rather than download to your local machine, you may need to edit the metadata on the file to indicate that this should happen. The property named Content-Disposition controls this. If it is set to:
attachment, the file will be downloadedinline, the file will be displayed within the browser
Although this may be subject to settings on some browsers, this is the basic setting you should check. Refer to Content-Disposition header (https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Disposition) for more information.
To see or edit the attributes, you will need an S3 application that makes them visible, such as:
Wasabi Explorer
In Wasabi Explorer, the page is:

Click Set HTTP Headers to access a screen that enables you to add, edit, or delete these attributes.

In the example above, the HTTP Header Content-Disposition is set as inline. You can edit this to attachment to change the behavior.
If you cannot find Content-Disposition in the list of headers, create one.
S3 Browser
In S3 Browser, the page is:

In the example above, the Header Content-Disposition is set as inline. You can edit this to attachment to change the behavior.
If you cannot find Content-Disposition in the list of headers, create one.