Chrome is one of Google's highlight products, as it reigns supreme as the browser of choice for a lot of people. Chrome's tight integration with Google services, and the fact that it comes preloaded on devices that have Google Play Store support allow it to be the default medium of interaction with the internet for millions of people every day.
Despite its popularity, Google Chrome is not perfect. There are a lot of areas where the browser can improve. Google themselves have recognized some of these issues, as community-requested features such as Dark Mode and "Never Slow Mode" are now in the pipeline for a wide release. Now, Google is adding support for PDF related features such as PDF Annotation and PDF Form Filling support to Chrome.
PDF annotations can be enabled in the Dev Channel of Chrome through the flag chrome://flags/#pdf-annotations, while PDF form filling is available as a flag in the Canary Channel, but has no attached feature at the moment (but is expected to be added in the future).
Once the flag for annotations is enabled, an additional pencil icon will be made available in the Chrome PDF viewer.
This icon houses the tools for an eraser, a pen, and a highlighter, each with 28 colors and 8 pen tip sizes to choose from. Since this is all web-based and does not require additional plugins or installations, these would be enough for most users to highlight errors or make other simple modifications to a PDF. Similarly, we expect PDF form filling functionality to also be available natively, without the need for any additional installation.