Adobe Acrobat Reader is free, and freely distributable software that lets you view and print Portable Document Format (PDF) files.

Acrobat Reader also lets you fill in and submit PDF forms online.

Adobe Portable Document Format
Invented by Adobe Systems and perfected over 15 years, Adobe Portable Document Format (PDF) lets you capture and view robust information - from any application, on any computer system - and share it with anyone around the world.

Adobe Reader software adds much new functionality, especially relating to collaboration, PDF file creation, security, and an enhanced user experience.

Improved launch speeds
Looking for faster launch speeds? Adobe has enhanced general performance and, in particular, has reduced launch times with Adobe Reader. Try it: You'll notice the difference.

PDF Portfolios
Packages, introduced in Adobe Reader, have been greatly enhanced and renamed. Portfolios provide easy navigation when you work with multiple PDF documents and other document types. They also enable you to work with a collection of materials such as drawings, e-mail messages, spreadsheets, and videos as a single file, which makes distribution, storage, retrieval, and collaboration easy for end users.

Native Adobe Flash support
Adobe Reader can natively display rich media content, which you'll notice immediately with Portfolios. Interested in viewing SWF and FLV files? Adobe Reader 9 is the answer.

Acrobat.com
Included with Adobe Reader is Acrobat.com (beta), an exciting new set of online services from Adobe. With Acrobat.com, you can create PDF files online; create and coauthor documents with others; host live web meetings; upload and share PDF files and other types of documents and control who has access to them; and even embed a rich, interactive preview of your document in a web page.

All of these services and more are provided online, so you can access them from anywhere. And you'll find easy access points from within Reader. As an added convenience, Acrobat.com leverages Adobe AIR, so you can interact with Acrobat.com from your desktop. Acrobat.com on Adobe AIR is a small application that is included with your download of Adobe Reader. Available in select languages.

Improved CAD and geospatial functionality CAD and geospatial functionality have been greatly enhanced in Adobe Reader. For instance, CAD designs or geospatial maps that have been converted to PDF offer Adobe Reader users access to CAD features, such as dimensions, or map features, such as longitude and latitude, for powerful collaboration and interaction.

PDF Standards Pane
When a PDF/A or PDF/X standard compliant file is opened, a Standards Pane appears and provides important file details.

Security enhancements
Adobe Reader provides new digital signature functionality for an improved user experience. The new version also adds support for 256-bit AES encryption.

Accessibility enhancements
Adobe Reader significantly improves the viewing of XFA forms for accessibility, while providing greater screen reader support.

Adobe Reader MUI
Adobe Reader MUI is Adobe's Multilingual User Interface version. This product is capable of installing any combination of supported languages. So, for example, you can install French, German, and Spanish simultaneously and then have the capability to switch among those languages within Adobe Reader. The user interface changes to the appropriate language on the fly.

A 3rd party speedup tool for Adobe Reader is also available. It disables many of the plugins that are not needed. It has an easy to use interface including a couple of speed options as well as restore to default. Download that here.