If you are a SharePoint Online user, then you are probably aware of the new guest link feature. When external sharing is enabled both for your tenant and the site collection in which you are working, you can grant users outside the organization access to individual documents in your site collection. Depending on the sharing options set by your administrator, you may be able to use guest links, which grant external users access to documents without those users having to provide credentials. When sharing the document, you just need to clear the Require sign-incheck box, as shown in the following figure.
When external users click to open the link that is in the body of the email notification message, the document will open in the appropriate Web App. Note that only “guest” information is displayed at the top right, where an account is typically shown.
If you have a Document Center in your site collection and you are attempting to use guest links for documents in that site, your external users might see the following error.
Originally, I thought the versioning settings in the Document Center library caused the error. However, when I recreated the same versioning settings (for example, enabling versioning and requiring documents to be checked out prior to editing) for the library that was not in the Document Center, I was not able to reproduce the error. Likely, there is something inherent to the Document Center site template that prevents external sharing for documents within it. For other site templates though, you have a powerful mechanism by which to share content anonymously.