I recently discovered that by default, document libraries in SharePoint don’t allow rich text columns on their list items. Whether added directly to the list, chosen from site columns or through a content type, rich text columns get demoted to just plain text when on a document library. This can be infuriating when you really need rich text (in my case, I was trying to construct a web page using the properties of a document to fill in placeholders in the document itself).
Don’t fret, though! It turns out there’s actually a really simple way to get your rich text column fully functional again on document libraries, and it doesn’t even require custom code or even forays into powershell. All that is necessary is SharePoint Designer.
You can open your site in SharePoint Designer then click the “All Files” option from the left navigation. This shows a listing of all the various lists/libraries and other items that reside on your site. From here you can right-click on the problem document library and select “Properties…” which will of course bring up the properties window for the document library.
From the properties page, you can click on the “Edit list columns” link under the Customization heading which will take you to a listing of the columns on the document library. Simply right-click the column that refuses to be rich text, select “Column Settings” and check the rich text box. Don’t forget to save the changes to the list when you’re done!