PDF format is an easy and ever-popular means for exchanging digital documents. However, unless you're willing to pay lots of money, the tools for working with PDFs are limited and sometimes cumbersome. For example, a simple typo often necessitates a time-consuming rework of the entire document.

Free software offers several rudimentary tools for generating PDFs. For example, OpenOffice and LibreOffice include an import filter originally from KOffice (now Calligra) that allows limited PDF editing (Figure 1), but the results are not always satisfactory.

Figure 1: LibreOffice exhibits significant weaknesses as a PDF editor.

If you're looking for a simpler and more powerful way to work with PDFs, you're better off with a PDF editor. PDF editors simplify the task of working with PDFs because they let you modify a document directly, without having to recreate it. Code Industry's Master PDF Editor [1] is a popular editing tool that displays the document in a way that is much closer to the printed version (Figure  2).

Figure 2: Master PDF Editor is far more accurate.

Hands On

Many distributions let you install Master PDF Editor directly from the respective package sources; this is the case with Arch Linux and Ubuntu and its derivatives. Alternatively, the manufacturer provides binary packages for 32- and 64-bit Linux machines free of charge (see the "Installation" box). For around US$  50 (EUR  40, UK£ 30), you can purchase a license that includes both support and a Windows or Mac license.

Editing with the program is simple: Instead of first converting the file to another format, Master PDF Editor loads it directly into a viewer. The process is much quicker than importing into one of the office programs, in which editing is done in the vector graphics component. Master PDF Editor is more like a word processor or desktop publishing software, as the structure of the main window reflects. The toolbars below the menus offer similar functions to those applications.

On the left side of the main window are four buttons that let you toggle between different modes: Pages gives you direct access to the pages in the document (Figure 3). To extract a number of contiguous pages from the document, use the function from the context menu in the sidebar to delete the preceding and following pages.

Figure 3: The left sidebar shows selected information for the loaded document. The editor refers to internal and external links in the file as Interactive.

The Bookmarks button shows the document structure, if the PDF supports this. Master PDF Editor can retrospectively change bookmarks, if needed. In the example shown in Figure 4, a new entry is added to the document at the desired location in the list of bookmarks using the Add Bookmark feature in the context menu. You can configure how exactly to display the bookmark in Options.

Figure 4: Master PDF Editor allows you to edit bookmarks or buttons, or provide them with various functions, retrospectively.

Bookmarks generally provide the ability to integrate various functions via Action. However, some documents in PDF/A format (a PDF subset for long-term archiving of digital documents) prevent this. Additionally, active content in PDF documents is a serious security issue, so you should use this feature with caution. In any case, not all PDF viewers on Linux will actually display such content correctly.

Newer versions of the PDF format (as of PDF 1.7) let you attach additional files to the document; you can extract and use these files later on. This feature is useful for source code, for example, that you describe step by step in the document and provide in full as a file attachment. In the sidebar, the Attachment entry shows the appended files. A context menu lets you to remove attachments or add new ones (Figure 5).

Figure 5: Newer PDF versions let users attach additional files to a document. Master PDF Editor can handle this and also replace or extract attachments.

The fourth button in the sidebar, Search, provides an advanced search feature: All matches in a document are displayed as a list. This means you can go directly to any match, as needed, and compare it with the previous one.

Editing

Master PDF Editor distinguishes between different document editing modes. Edit Document lets you modify parts of the document, such as lines of text, images, or interactive elements. Double-clicking one of these objects pops up a dialog. Edit Text lets you change the aspect of the text, such as fonts, colors, and attributes.

You can use the Hand Tool to move pages, open links, and select text passages. Select Text lets you highlight parts of the text that you then edit. To toggle between these modes, use the keyboard shortcuts Alt+1 through 4; alternatively, you can select the functions in the Tools menu. Table 1 lists other important keyboard shortcuts.

If you just want to correct some spelling mistakes, for example, just double-click the appropriate line or word and then you can edit the text. However, the editor here uses the previously configured character set. Because PDFs typically only embed the characters of a font that are actually used, you might see the error message shown in Figure 6 if you are unlucky.

Figure 6: The editor only has access to the (sub)fonts embedded in the document.

However, Master PDF Editor also lets you modify the current font for selected areas. The typical aspects of a font (bold, italic, and the combination of both) are set using the lower of the two toolbars. You can also adjust the current font size and the color used. In the fields to the right, you can configure the stroke and shape of the text. You can also use the Stroke feature to change the outline of a font to a different color.

Furthermore, the current version of the tool only lets you change the fonts for entire lines if they are located in a box. The developers want to remove this limitation in a future release.

In some cases, PDF documents consist of many objects on a page. This design allows for special effects, but occasionally causes problems during post-processing if the objects overlap in the wrong order. Master PDF Editor provides buttons to fix this (Figure 7).

Figure 7: If needed, you can delete the selected items or move them to the background or foreground.

Images and Notes

Master PDF Editor lets you extract images quickly and easily from PDF documents; you can replace the images or even add new ones. If you select the desired image in edit mode (Alt+1), you can Save as image via the context menu. Pressing the Del key deletes the image, and Ctrl+I inserts a new image. You can change the image size using handles on the frame.

Selecting File | Export lets you save individual pages or the entire document as an image. The results here are significantly better in quality than converting with ImageMagick, and the resulting file is more compact.

Even the Okular PDF reader from the KDE collection is capable of creating notes and highlights in PDFs (see the "Commenting PDFs with Okular" box). However, Master PDF Editor simplifies this job decisively: You can place your notes directly in the document and forward the document with your annotations in place. You create a note by selecting Notes | Add comment. To do this, you can draw a box that can even store extensive texts (see Figure  8).

Figure 8: Notes are added directly to the document and bundled with the document.