59214 Best iPad PDF Readers Werner Ruotsalainen iPhone Life 1528-5456 2010-09-23 NovDec2010_BuyersGuide 2 5 29 Apps Business

The iPad, with its gorgeous IPS screen, is particularly well suited for eBook reading. No wonder there are a lot of excellent PDF readers and even some annotator apps available for the platform. In this article, I look at the five top PDF readers and compare important features.

•  iBooks by Apple (free, iPad and iPhone versions, app2.me/2403),

•  iRead PDF by Aji Ltd (free, app2.me/2920),

•  iAnnotate PDF by Aji Ltd ($9.99, app2.me/2921),

•  ReaddleDocs by Igor Zhadanov ($4.99, app2.me/2922; iPhone version, app2.me/2923), and

•  GoodReader by Yuri Selukoff ($0.99, app2.me/2924; iPhone version, app2.me/2925).

Important features

Let's take a quick look at some of the more important PDF reader features and show how these apps implement them.

Searching for information

imageIf you plan to use your iPad as a collection of searchable books, you will certainly welcome some of the more advanced PDF readers. Except for Apple's iBooks, all of these readers have a search feature. The iRead PDF app even allows you to search for words throughout your entire PDF library. This is of great help when you quickly need to remember which book discusses a particular subject.

iRead PDF lets you search for words throughout your entire PDF library.

Locking documents for security

I frequently loan my iPad to friends at work so that they can browse the Web while I'm working. When I do this, I prefer to lock out access to my PDF library. Of the five apps listed, only iBooks and iRead PDF do not allow you to do this. GoodReader even allows you to have separate passwords for each folder, in addition to generic startup authentication and re-invocation if you go to GoodReader when it's running in the background.

Adjusting backlight for easy viewing

imageUnfortunately, the screen of the iPad can be too bright even when using the minimal backlight level. All of these advanced PDF readers allow you to decrease the backlight level beyond the normal limits of the iPad.

GoodReader (above) and ReaddleDocs can display two pages in landscape viewing mode.

Displaying two pages in landscape view

GoodReader and ReaddleDocs both allow you to display two pages at the same time when your iPad is in landscape mode. While the resolution may not be sufficient for easy readability, it's a good feature for some user manuals and technical books that have illustrations that carry over to another page.

Keeping multiple docs open at the same time

imageOnly iRead PDF and iAnnotate PDF can keep multiple PDF files opened at the same time (up to six). This makes it easier to switch between documents.

iimageAnnotate PDF (left) offers the best text/drawing annotation. ReaddleDocs (right) also lets you add textual annotations with ReaddleDocs.

Highlighting and annotating text

iAnnotate is the PDF reader with the best text/drawing annotation features (it's pretty close in capabilities to its desktop counterparts). With iAnnotate PDF, you can zoom in on a page, add a drawing or handwritten annotation, and zoom out. This lets you create pretty decent annotations using your finger.

The most recent version of ReaddleDocs has annotation (notes) capability. iBooks allows you to add notes to eBooks but not to PDF files. Some other readers offer lower-level annotation support. For example, SmileyDocs 1.6 ($0.99, app2.me/2943) lets you highlight and add notes, but they are only displayed in the view they are created in (same orientation and same zoom level).

Table of Contents (TOC) support

All PDF readers, except Apple's iBooks, support TOCs, which help you find what you're looking for and navigate to it quickly. (iBooks supports TOCs in eBooks but not in PDF files.) ReaddleDocs has the best TOC implementation, displaying subsections with correct indentation. The other apps in this article only show one level of the TOC.

Thumbnail view of pages

imageimageA thumbnail view of pages in a PDF document can help you find things that may not be mentioned in the TOC, including illustrations, charts or tables, color inlays, etc. iBooks is the only one of the PDF readers in this article that will display thumbnails. It not only displays the TOC as thumbnails, it displays a thumbnails view of the page you are on and subsequent pages at the bottom of each page.

iBooks displays the TOC as thumbnails and has a small thumbnail strip at the bottom of each page.

More features; more PDF readers

These five PDF readers are the best available for someone needing a powerful, full-featured app. If you're looking for something simpler (and with far fewer features) check out SimplyPDF ($1.99, app2.me/2927).

This article describes only some of the advanced features found on these five PDF readers. For more information on them and 30 other titles, check out my article titled,"The Ultimate PDF Reader Roundup" located on the iPhone Life blogs (iphonelife.com/blog).