Open PDF file using swift

For Xcode 8.1 and Swift 3.0

Save the PDF file in any folder of your xcode. Suppose the file name is 'Filename.pdf'

if let pdf = Bundle.main.url(forResource: "Filename", withExtension: "pdf", subdirectory: nil, localization: nil)  {
    let req = NSURLRequest(url: pdf)
    yourWebViewOutletName.loadRequest(req as URLRequest)        
}

Same will apply if you want to open any html file.

If you simply want to view a PDF file you can load it into a UIWebView.

let url : NSURL! = NSURL(string: "http://developer.apple.com/iphone/library/documentation/UIKit/Reference/UIWebView_Class/UIWebView_Class.pdf")
webView.loadRequest(NSURLRequest(URL: url))

Swift 4.1 :

let url: URL! = URL(string: "http://developer.apple.com/iphone/library/documentation/UIKit/Reference/UIWebView_Class/UIWebView_Class.pdf")
webView.loadRequest(URLRequest(url: url))

If you'd like to achieve more, a good framework is PSPDFKit.

SWIFT 4+

If has to open file from local cache/Documentdiectory which has file path

Method 1: using UIDocumentInteractionController

class ViewController: UIViewController,UIDocumentInteractionControllerDelegate {
   //let path =  Bundle.main.path(forResource: "Guide", ofType: ".pdf")!
    let dc = UIDocumentInteractionController(url: URL(fileURLWithPath: path))
    dc.delegate = self
    dc.presentPreview(animated: true)
}

//MARK: UIDocumentInteractionController delegates
func documentInteractionControllerViewControllerForPreview(_ controller: UIDocumentInteractionController) -> UIViewController {
    return self//or use return self.navigationController for fetching app navigation bar colour
}

Method 2: using WebView

let webview = WKWebView(frame: UIScreen.main.bounds)
view.addSubview(webview)
webview.navigationDelegate = self
webview.load(URLRequest(url: URL(fileURLWithPath: path)))//URL(string: "http://") for web URL

Apple added PDFKit framework in iOS 11

Add a UIView to your view controller and make it's class to PDFView

import UIKit
import PDFKit

class ViewController: UIViewController {

    @IBOutlet var pdfView: PDFView!

    override func viewDidLoad() {
        super.viewDidLoad()

        if let path = Bundle.main.path(forResource: "sample", ofType: "pdf") {
            if let pdfDocument = PDFDocument(url: URL(fileURLWithPath: path)) {
                pdfView.displayMode = .singlePageContinuous
                pdfView.autoScales = true
                pdfView.displayDirection = .vertical
                pdfView.document = pdfDocument
            }
        }
    }
}

There are 4 display modes : singlePage, singlePageContinuous, twoUp, twoUpContinuous .