Apple has released small updates for all of its operating systems to address bugs and security concerns. Apart from Sierra users who have experienced problems with PDFs, most users will be best served by delaying updates.
macOS 10.12.3 Sierra -- The update includes just a few notable fixes. Preeminent among them is a fix for the bug that caused Preview to delete OCR text layers when editing a PDF (see “ ,” 2 January 2017). The update also promises to resolve a compatibility issue with PDF documents that have been exported with encryption enabled.
Unfortunately, early reports from developers indicate that many other problems with PDFKit remain; Michael Tsai of C-Command said that he is still seeing previously reported user interface and rendering bugs. For instance, open a PDF in Preview, choose Tools > Rectangular Selection, draw out a selection, and press Command-C — you’ll see a horrible display bug that appears to delete the entire page until you click again.
Apple also claims that the 10.12.3 update:
Improves automatic graphics switching on the MacBook Pro (15-inch, October 2016).
Resolves graphics issues while encoding Adobe Premiere Pro projects on the MacBook Pro with Touch Bar (13- and 15-inch, October 2016).
Fixes an issue that prevented some third-party applications from correctly importing images from digital cameras.
macOS 10.12.3 is a 1.05 GB update available via Software Update. Alternatively, you can instead download a (for 10.12.2, 1.28 GB) or  (from any version of 10.12, 2.04 GB). If you’ve had PDF problems with Sierra, you probably want to install it right away. Otherwise, hold off for a few days to see if any major issues are reported online.
The update also includes.
iOS 10.2.1 -- Release notes for the iOS 10.2.1 update are minimal: “…includes bug fixes and improves the security of your iPhone or iPad.” However, there are in the update. The update — 67.4 MB on an iPhone 7 Plus — can be obtained via Settings > General > Software Update or from iTunes.
Since it doesn’t appear to be a major update, we recommend holding off on updating to iOS 10.2.1 for a week or so to be sure that no problems crop up.
tvOS 10.1.1 -- You can obtain the tvOS 10.1.1 update on your fourth-generation Apple TV via Settings > System > Software Updates > Update Software. Other than, we know nothing about the update, but can assume that it contains small bug fixes. If your Apple TV is working fine, there’s no need to update immediately, but it’s probably worth installing next week sometime if no problem reports appear online.
watchOS 3.1.3 -- Like the iOS and tvOS updates, the watchOS 3.1.3 update has minimal release notes, other than. The 126 MB update can be found in Watch > General > Software Update on your iPhone. Remember that upgrading requires your Apple Watch to be in range of your Wi-Fi–connected iPhone, connected to its charger, and charged to at least 50 percent. The update will likely take longer than you expect, so allot at least an hour.
Given that the watchOS 3.1.1 update bricked a number of Apple Watches, and was later withdrawn and rereleased by Apple, we recommend holding off on the watch OS 3.1.3 update for at least a week, if not more.