Instapaper, Dropbox, GoodReader, and Simplenote are my favorite applications for reading, writing, and sharing documents on the iPhone and the iPad. I have used each application for more than six months and I highly recommend all of them.

Instapaper

The Instapaper application makes it simple and pleasant to read lengthy articles on your mobile device. Instapaper is optimized for the type of articles where you find yourself starting in your browser and thinking, “I’d rather read this later”. The application automatically loads any new content from the Instapaper Web service, which reformats Web pages for small screens and strips away unnecessary elements. The service provides an experimental option to save pages formatted for the Kindle as well.

There are multiple ways to save content to the Instapaper service including a bookmarklet, email, or applications that integrate Instapaper directly. The “Read Later” bookmarklet is compatible with most desktop browsers, mobile browsers and Google Reader. Each Instapaper user receives a unique email address that will import included links and text. Many iPhone and iPad RSS feed readers, Twitter clients, and social bookmark clients support saving links to Instapaper directly. The Instapaper service allows sharing of individual articles via email, Tumblr, and several Twitter clients.

Instapaper is available in two versions, a free ad-supported version with a limit of 10 articles, and a $5 (USD) pro version with a 250-article limit. The pro version includes additional features, such as background updating, folders, remembering the last read position, tilt scrolling, multiple font options, and disabling rotation. I find that the pro version is well worth the price.

Dropbox

In a crowded market of Web-based consumer storage services, Dropbox is popular and widely praised. The minimal user interface of the desktop application is one reason for its popularity. When I say minimal user interface, in most cases I mean non-existent. This is the beauty of Dropbox. After installing the application, Dropbox appears as a folder on your desktop. The folder is essentially magic. Any files in the folder are automatically synchronized to all other machines where you have Dropbox installed. Mobile Dropbox clients synchronize with the server upon launch. In my experience, it just works, and this is high praise. Dropbox is fully accessible via a Web interface for devices without an installed Dropbox client. Dropbox saves any revisions to your files for 30 days by default. These revisions are only available via the Web interface and do not count against your storage quota.

Working with shared files on Dropbox is as easy as working with files on the desktop. Shared files and folders are synchronized with all authorized users’ accounts. My only real complaint is that sharing must be configured from the Dropbox Web interface rather than a Dropbox client, which is not intuitive. Access control for sharing is based on email addresses and can only be configured via the Dropbox Web interface. It is important to recognize that any shared files count against the storage quota for all shared accounts. Each user’s Dropbox folder has a public directory—any files placed in that directory become publicly accessible without access control. The mobile Dropbox can generate links and can be used to share individual files with any email address. Be careful, the mobile links can also share private files and currently there is no way to revoke access.

Another reason for Dropbox’s popularity is its broad platform support. Mobile clients for Dropbox are available for the iPhone, iPad, and Android devices. A BlackBerry version is in development. Desktop clients are available for Mac, Windows, and Linux. All Dropbox clients are free. The mobile Dropbox client takes advantage of the document viewers built that are part of iPhone OS to open files directly. Supported formats include plain text, RTF, Microsoft Office documents, iWork documents, PDFs, Web pages, images, music files, and videos. Dropbox only supports viewing files; files must be edited with another application.

Some mobile applications such as GoodReader can read and write files from the Dropbox service, although the process is a little convoluted. Dropbox recently added a new mobile API to allow iPad applications to easily save files to a Dropbox account. Saving files to Dropbox is far easier with the most recent version of the GoodReader iPad application due to the new APIs. Even better, the Dropbox iPad application allows you to open files directly in other applications. Hopefully the iPhone Dropbox application will gain this functionality with the next major version of iPhone OS.

Dropbox is a subscription service that uses the Amazon Simple Storage Service (S3) for the backend store. A free account is available with 2 GB of storage. There are two paid upgrade options—a 50 GB option for $10 (USD) a month or $100 (USD) a year and a 100 GB option for $20 (USD) a month or $200 (USD) a year. Paid accounts can optionally save file revision history forever.

GoodReader

GoodReader works well with long and complex PDF documents. I have used it to read PDFs that are several hundred pages long without a problem. The iPhone and iPad support PDF files natively, but navigating long documents is cumbersome as there is no support for jumping to a specific page, for using PDF bookmarks and outlines, or for searching PDF files. GoodReader supports navigation to specific page numbers, PDF bookmarks and outlines, and full text and bookmark-based search. The application includes a night mode for reading in the dark and an autoscroll mode for reading long files without having to manually select the next page.

GoodReader’s support for text files includes a number of features not available in the native viewer, including the ability to edit text files and reflow text when the font size changes or the device is reoriented. One feature, called PDF Reflow, extracts plain text from PDF files and displays it in GoodReader text file viewer so it can be reflowed, copied to the clipboard, or edited. PDF Reflow should not be confused with accessible PDFs that are sometimes called reflowable PDFs.

GoodReader supports file transfer over WiFi in addition to many storage services including POP and IMAP email servers, WebDAV servers, Apple’s MobileMe, Dropbox, Box.net, Google Docs, and FTP servers. There are two versions of GoodReader for the iPhone. The standard version is $0.99 (USD). Access to POP and IMAP email servers, Google Docs, and FTP servers require a $0.99 (USD) in-app upgrade purchase each. GoodReader Light includes all available types of server access and is available for free on the iPhone, however it is limited to storing five files. GoodReader for the iPad is currently on sale for $0.99 (USD) and includes all available types of server access.

Simplenote

Simplenote is a note taking application for the iPhone and iPad that automatically synchronizes with the Simplenote Web service. The application has a basic feature set, but it works very well and is easy to use. Notes are stored as plain text and can be forwarded as email messages or deleted individually. Unfortunately, there is no mechanism to work with multiple notes at once. The built in search is fast and searches incrementally as you type, to quickly narrow down the list of notes with the search term. Options include changing the sort order, preview, link detection, and display of file modification dates. If the user has installed TextExpander, snippets will expand automatically. All notes can also be viewed or edited in any Web browser using the Simplenote Web service.

Currently, support for the iPad is limited to the same feature set as the iPhone aside from running in full screen mode. The developer plans to add additional iPad specific features shortly. The Simplenote API enables synchronization with multiple desktop applications including Notational Velocity—a simple, fast, stable note taking application for Mac OS X. This means I can create notes, make changes or additions either on the desktop or my iPhone and they are automatically synchronized. I am very happy with the setup.

Simplenote is free and ad-supported. A $9 (USD) a year premium add-on removes ads, provides an automatic backup, an RSS feed, the ability to create notes by email, access to beta versions, and prioritized support.

* This article originally appeared as Great iPhone and iPad Apps for Reading and Sharing Docs in the May 2010 issue of Messaging News.