When Microsoft rolled out its Windows 10 Mobile Patch Tuesday updates last month (on a Wednesday), there was a known issue for those that are on the Creators Update (version 1703) and the Fall Creators Update (version 1709): PDF rendering was broken in the Edge browser. When this month rolled around, an update was released for those on version 1709 fixing the issue, but other supported versions of the OS - 1607 and 1703 - didn't receive any updates at all.

Today, the March update is finally rolling out for phones that are stuck on version 1703. These should really only include Lumia 640 and 640 XL devices, as those were the only phones that were supported for the Creators Update, but not for the Fall Creators Update.

Here's the full changelog for KB4088782, or build 15063.966, which contains the fixes for PCs as well:

Addresses issue with printing XML documents in Internet Explorer and Microsoft Edge.

Addresses issue where Internet Explorer stops working when using F12-based developer tools.

Updates legacy Document Mode cell visibility in Internet Explorer.

Addresses issue where Internet Explorer is unresponsive in certain scenarios when a Browser Helper Object is installed.

Addresses issue that causes online video playback to stop responding.

Addresses issue where, after installing KB4056891, KB4057144, or KB4074592 on a server, you may not be able to access SMB shared files in directory junction points or volume mount points hosted on that server. The error is "ERROR_INVALID_REPARSE_DATA”. As a result, editing some group policies using GPMC or AGPM 4.0 may fail with the error "The data present in the reparse point buffer is invalid. (Exception from HRESULT: 0x80071128)".

Due to recent work with our antivirus (AV) partners, AV software has now reached a sustained level of broad compatibility with Windows updates. After analyzing the available data, we’re lifting the AV compatibility check for the March 2018 Windows security updates for supported Windows 10 devices through Windows Update. We’ll continue to require that AV software be compatible. Devices with known AV driver compatibility problems will be blocked from updates. We recommend that customers check installed AV software compatibility with their AV provider.

Addresses issue in which WPF applications that are running on touch or stylus-enabled systems may stop working or stop responding after some time without any touch activity.

Addresses issue in which PDFs cannot be rendered in Microsoft Edge on Windows 10 Phones.

Security updates to Internet Explorer, Microsoft Edge, Microsoft Scripting Engine, Windows Desktop Bridge, Microsoft Graphics component, Windows Kernel, Windows Shell, Windows MSXML, Windows Installer, and Windows Hyper-V.

As always, you can install today's update by going to Settings -> Update & security -> Phone update -> Check for updates.