A common support question that’s been popping up on the web after WordPress users update to 3.9: What happened to the “Paste from Word” button in the visual editor? If you find that the button is missing, don’t worry – it’s not a bug. Prior to this update, the button was located in the kitchen sink of the visual editor:
WordPress 3.9, however, removes the “paste from word” button entirely. It includes TinyMCE 4.0 and has better built-in support for pasting in blocks of text for Microsoft Word. The better your software gets, the more the magic happens behind the scenes. WordPress now detects if the pasted text is coming from MS Word and makes the appropriate changes.
Until I saw the question on Reddit, indicating that the button had gone missing, I had no idea that anyone still used this feature. The missing button is actually an enhancement, not a bug. Hopefully this information has reached you before you started deactivating all your plugins.
Via Jeff Domansky