While working on a PDF reader application for iOS I had to dig up a lot of information on the web. Having completed the same I am putting down various options I found:

1. Starting with an easy method, Using UIWebView.

UIWebView *webView = [[UIWebView alloc] initWithFrame:CGRectMake(10, 10, 200, 200)];NSString *path = [[NSBundle mainBundle] pathForResource:@"document" ofType:@"pdf"];
NSURL *targetURL = [NSURL fileURLWithPath:path];
NSURLRequest *request = [NSURLRequest requestWithURL:targetURL];
[webView loadRequest:request];[self.view addSubview:webView];

Using the above code we can see the PDF document stored in a directory will be displayed in the web view.

2. Using VFR Library to quickly access, display, and browse PDF documents within our own applications.
Features like sliding PDF pages, displaying PDF pages at the bottom are available using this library.
Click on this link to get more details.

3. Using Leaves which is an open-source iOS component that simulates a page-turning transition between content views, much like the transition found in Apple’s official iBooks application.
Click on this link to get more details.

4. Using an open source framework called FastKitPDF.
Here we are having plenty of features such as searching text, zooming etc.
Click on this link to get more details.