More and more operating systems, smartphones, and other devices contain built-in abilities to show PDF files; even your web browser can probably handle it. Even so, a dedicated document reader often has a number of advantages over the built-in reader you may already have, like viewing options, better search, and annotations or other light editing. Different types of viewing modes are available, like Single Page, Facing, Book View, and Presentation. The latter view is great for distraction-free reading. There are tons of keyboard shortcuts you can use that make it easier to move around a PDF file, which you can refer to in the online documentation. You can download SumatraPDF in portable form or install it like a regular program. Tons of features are included: Take snapshots of text and images, view the PDF in Read Mode for a more concise reading pane, and have the program read text out loud. This program works with Windows, Mac, and Linux. The Adobe Acrobat Reader mobile app is available for Android and iOS. Click the top left program icon on MuPDF’s title window, then select About MuPDF to see all the supported shortcut keys you can use to flip through pages, zoom in, and search for text. The other way to use this program is with an initial menu. Open mupdf-gl.exe from the same download to use that version. There are also advanced options like signing and adding text to the PDF. You can also highlight text, which is great if you’re using a PDF for study notes or a reference document. In addition to opening a PDF from your own local computer, you can also enter a URL of a PDF file (the document will still be downloaded, but the program does it for you). You can also add notes, record and attach audio, highlight text, attach files, and add a strike-through to words. This is for Windows versions all the way back to Windows XP. This program also lets you send the currently opened PDF to someone over email with the Email toolbar button. Sorax is available for Windows. Everything is spotless and easy to read and understand. The search feature isn’t the best to be had, but it works well as is. It can launch a PDF in full screen to make reading easier, and you can just click the screen to move down the PDF pages. This PDF program runs on Windows, Mac, iOS, and Android. While it might not require much disk space, it’s not the best option available. There isn’t a search function, and scrolling isn’t the smoothest. However, it still works as a free PDF reader if you don’t like the others on this list. You can install Cool PDF Reader to your computer or use the Standalone Package to use it without installing anything.