If a file failed here before, it is worth dropping it in again. Three specific things were fixed in this update, and each of them was the kind of failure that looks like a broken document when it is really a broken renderer.
Arabic documents now lay out correctly
This is the one worth explaining, because "Arabic support" sounds like a language pack and it is not. It is typography.
Arabic letters change shape according to where they sit in a word — an initial form, a medial form, a final form, an isolated form — and they join to the letters beside them. A renderer that treats text as a straight sequence of characters and draws each one in its standalone shape produces something a reader recognises instantly as wrong: letters standing apart that should be joined, in a word that is still technically spelled correctly.
Then there is direction. The paragraph runs right to left, but a product code, a URL or a year inside that paragraph runs left to right, and the two have to be resolved against each other line by line. Get it wrong and a sentence comes out with its fragments in the wrong order.
The word-processing engine behind DOC, DOCX and ODT was updated, and both of those are handled properly now. If you have an Arabic document that came out as disconnected letters, that document renders.
PDFs that were never saved to disk
Some PDFs are not files at first. A program builds one in memory and hands it straight on — an invoice generated by an accounting system, a report a web application produces on request. There was a bug in that path, and a PDF that arrived that way could fail to load while the same document saved to disk opened fine.
That is fixed. If you are the person generating those PDFs in your own code, this was the byte array path, and the same fix is in the component at Doconut.com.
Large PSD, ICO, EPS, TGA and WebP files finish
The image engine was rebuilt to hold less of a file in memory while it works. In practice that means the large design files that used to run out of room part way through now complete: a layered PSD from a real project, an uncompressed TGA, a high-resolution EPS.
Nothing about the formats changed. What changed is the ceiling you hit before the render finished.
EML and MSG
Email files open more reliably than they did — the saved messages people export from Outlook and then cannot read on a machine without Outlook.
If one of these was your file, the viewer is where to try it again.