UnionStation Viewer (U Viewer) is a tool used to examine and visualize the internal data structures of many types of files, backed by UnionStation library. Acrobat and other viewer applications shows the page graphics on screen, but U Viewer opens the PDF document as if it were a ZIP package with internal “folders” and “files”. These are virtual organizations that are conceptually similar to the disk file system structure, yet it comes handy when you can refer to a certain item with a distinct virtual path, and when you can directly operate on the item in a similar fashion, be it a page, an image, or a font. Many convenient functions are defined for specific types of objects, for example, a PDF page exposes actions on import, export, flattening, extraction, convertion, etc. In addition, data can be visualized in a variety of powerful ways.

• Explorer Style

  The screen layout resembles a Windows Explorer interface. The “address bar” shows the current path digging into the opened document. A data object is a file-like item, or a folder-like collection of items. In many cases, an item can be treated as both. The arrows are drop-down menus to facilitate jumping to another “folder” directly.

  To open a file, click the corresponding button, or drag a file elsewhere and drop it in the “address bar”, or paste the file's full path name there directly. Moreover, you can specify a virtual path to access an internal “folder” directly. Even embedded resources such as fonts could be opened and further explorable. More than one file can be opened simultaneously.

  You can also paste a web URL starting with “http://” and ending with “.pdf”. The file will be downloaded before opening.

• Listed Items

  Currently selected collection of items are listed in an auto-paginated list view, at most one thousand items per page. The list can be sorted, grouped, and filtered.

  Items of heterogeneous types can be listed in a single table. The columns are automatically constructured.

  There are two advanced views of the list: datagrid view launches and fills a data table, where you can copy the properties values as CSV; and an image browser of all image-type items with thumbnails in current collection, where you can batch export.

  There is also a search box, with which you can search the properties of all items for an interested keyword.

  Moreover, you can open a new tab for a collection, to avoid having to switch back and forth and get lost in the lists. Just right click on a collection and choose from the shortcut menu.

• Virtual Paths

  The virtual path inside a document resembles the in-page locators in HTML. That is, a ‘#’ sign followed by the collections along the way.

  Where there are multiple collections on the same level having the same name, a subscript is automatically used, ensuring that a path unambiguously refers to a collection that's of interest.

  This path can be bookmarked so that next time you can open this collection directly, without having to migrate along the way, step by step. The same path works on the given file wherever you open it, which means while you send a PDF file to someone else you can also include the path name in the email so that the receipient can access the same collection that you are talking about.

• Visualizers

  Right-click on any item to open up a list of available visualizers, which changes depending on the type of item being selected. Each will add a new tab into the visualizers area. There are four standard visualizers: bytes, image, text, and XML. An item can be visualized in any number of ways.

  An item could also come with its own customized visualizers. The user interface will query the item to list the available custom visualizers for you. For example, you can view the page's or form's rendered content, and view the document structure in a tree form.

  Text visualizer comes with syntax highlighting, which supports common languages such as Javascript, Postscript, XML -- which are common in PDF files nowadays. Both text and image visualizers support data extraction, meaning that you can save the content as a separate disk file.

• Properties

  The properties of a selected item is automatically loaded into the Properties tab at the left-hand side. Aside from custom properties, there is usually an expandable entry called “Data” that shows the raw PDF object data. This property grid is advanced in that the data of an indirect object such as “#115” can be loaded in another similar grid in a pop-up window, if you click the drop-down arrow beside it.

  The properties grid can list useful information that is hard to perceive otherwise. For example, it can show the encoding table of a font in a two-column table. It is also possible to change the value of a property.

• Actions

  An item defines what you can do with it, and the user interface list the retrieved actions for you in the Actions tab. Choose an action, and then hit the big button above. However, some actions come with parameters that must be set before running. For example, you need to specify the password for the “Encrypt” action, or you need to specify a file location for the “Save embedded font” action.

  And there are group actions, too! That is, multiple items of the same type can together execute a single action, for example, extracing several selected pages into a single output PDF file.

  Moreover, things can be done even more easily. You can drag an item and drop it onto the desktop or any folder to save it as a disk file. An image will become a TIFF file, a page will become a single-page PDF document, an embedded TrueType font will become a TTF file, and a collection of pages will be combined into a single PDF. Isn't it unmatchably handy and smart?

• Other Features

  Visited files are recorded, similar to what a web browser would do. The history list is optimally abbreviated to show the file names. The list can also be sorted. Unresolvable file specifications can be removed, and the entire history list can be wiped clean, too.

  The VirgoViewer comes with a free edition, and a licensed edition for commercial use, which unlocks some advanced features, such as:

  * Filling out a PDF form using values passed via CSV.
  * Converting all pages into a multi-page, full-color TIFF file.
  * Adding encryption to or removing it from a PDF file.
  * Import selected objects into XML or import it into another PDF file.