The Portable Document Format (PDF) [1], published by Adobe in 1993, quickly became the standard for exchanging electronic documents. Today, you can choose from a large selection of viewers for the Linux desktop.

In this article, I discuss 10 user-friendly and flexible PDF readers. In addition to standard functions, such as full-text search and bookmarks, the test team looked at the tools for marking and commenting. We also checked whether the readers can fill out forms and display file attachments. Table 1 summarizes the results.

Atril

Atril emerged from the Evince PDF viewer in 2011 and displays PDF, PostScript (PS), and EPUB files. Evince was the standard reader under Gnome 2.x at that time. Atril [2] is part of the Mate desktop [3] but is also available as a standalone application. The program usually appears in the Applications | Office menu. The interface is divided into three parts: In addition to the menu at the top and the toolbar at the bottom, a thumbnail previews the pages of the opened document on the left and the display area on the right.

Atril offers some additional functions. For example, it has a bookmark feature that is especially useful for large documents. The software also offers full-text searching and displays the results in green. In presentation mode, the reader takes up the entire screen and is controlled with the keyboard. Alternatively, a Bluetooth controller can be used.

To insert comments and text markers into the document, you open the Thumbnails drop-down menu and select Annotations. In the left bar, Atril replaces the thumbnails with the List tab, which displays the annotations. New annotations can be added to the PDF from the Add tab with the pencil icon. The mouse pointer becomes crosshairs, with which you select the desired location to place the comment. Atril then displays a yellow balloon and opens an input box with the name of the user (Figure 1).

Figure 1: Atril offers a comment function enabled by the small pencil icon.

You can stop annotating by clicking on the pencil icon again and then closing the input window. The speech bubble remains visible at all times, and double-clicking it reopens the annotation. If you want to save the document and its comments, use the Save copy option from the File menu. After reopening, the left sidebar displays the comments along with the page number, date, time, and name of editor, if the List tab is enabled.

The viewer also fills out forms by clicking on the form fields. The selected field then turns into an input line where you can type your text.

Evince

The default viewer on current Gnome desktops is Evince [4]. Although its functionality is similar to Atril, the developers have visually adapted the reader to the conventions of Gnome 3.x. Therefore, you will no longer find a menubar, and the few buttons are integrated into the titlebar (Figure 2). Much like Atril, the left column displays thumbnails for quick navigation, comments, and attachments.

Figure 2: Evince is the PDF viewer of current Gnome work environments and visually matches the desktop.

Comments and colored marks can be added to the document by clicking on the pencil icon. Evince also displays annotations, bookmarks, and markup from other programs without complaint. If you have added an attachment to a PDF, the reader can display the attachment and, depending on the file type, use a different Gnome program for viewing.

Evince can fill out and save PDF forms, although significant latency and display errors occurred during input. However, the completed forms were fine after saving and could be opened in other readers.

Foxit Reader

US-based Foxit Software has been developing and maintaining its Foxit Reader [5] since 2001 and offers it as freeware for free download. The manufacturer advertises it as a lightweight alternative to the sluggish Adobe Reader and provides a Linux edition (32- and 64-bit) for download. After unpacking the archive, you call a script that integrates the reader into the system with the help of a wizard and creates suitable menu entries.

Some older versions were noticeably impaired by ads and, above all, by security gaps, but the manufacturer has generally overhauled Foxit Reader and modernized its appearance. The program impresses with a tidy interface. A column on the left side offers quick access to documents, and thumbnails on the right show previously opened files.

The toolbar supports quick access to the navigation elements and searching. The three buttons, View, Comment, and Connect, open menus with frequently used functions. Foxit Reader is one of two test candidates that arrange new documents in tabs. If you miss the page preview thumbnails, you can enable the feature with View | Navigation Panels | Pages. The View menu also provides access to functions for rotating, enlarging, and reducing PDFs.

Foxit Reader shows its full potential when editing documents. Besides bookmarks, comments, and markers, the program also adds attachments to open files. Clicking on the paper clip in the left column displays and opens attachments. The program is not limited to the PDF format; it also stores audio and video. The reader does not open foreign formats; you save them with a right-click by choosing Save attachment as.

The test team was impressed with the comment function: Foxit Reader not only contains tools for commenting, but for crossing out, underlining, circling, and more. You can choose from several colors and geometric shapes (Figure 3). In forms, the program highlights fields that allow text entry in light blue and enters the letters directly into the boxes.

Figure 3: Foxit Reader offers many tools for marking parts of PDF documents or adding comments.

The Connect button provides functions for collaborative work, for which a free account and a commercial cloud connection to the manufacturer are required.