How to download PDF and store it locally on iPhone?

I have found one method which I tried myself:

// Get the PDF Data from the url in a NSData Object
NSData *pdfData = [[NSData alloc] initWithContentsOfURL:[
    NSURL URLWithString:@"http://www.example.com/info.pdf"]];

// Store the Data locally as PDF File
NSString *resourceDocPath = [[NSString alloc] initWithString:[
    [[[NSBundle mainBundle] resourcePath] stringByDeletingLastPathComponent]
        stringByAppendingPathComponent:@"Documents"
]];

NSString *filePath = [resourceDocPath 
    stringByAppendingPathComponent:@"myPDF.pdf"];
[pdfData writeToFile:filePath atomically:YES];


// Now create Request for the file that was saved in your documents folder
NSURL *url = [NSURL fileURLWithPath:filePath];
NSURLRequest *requestObj = [NSURLRequest requestWithURL:url];

[webView setUserInteractionEnabled:YES];
[webView setDelegate:self];
[webView loadRequest:requestObj];

This will store your PDF locally and load it into your UIWebView.

In Swift 4.1

// Url in String format
let urlStr = "http://www.msy.com.au/Parts/PARTS.pdf"

// Converting string to URL Object
let url = URL(string: urlStr)

// Get the PDF Data form the Url in a Data Object
let pdfData = try? Data.init(contentsOf: url!)

// Get the Document Directory path of the Application
let resourceDocPath = (FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)).last! as URL

// Split the url into a string Array by separator "/" to get the pdf name
let pdfNameFromUrlArr = urlStr.components(separatedBy: "/")

// Appending the Document Directory path with the pdf name
let actualPath = resourceDocPath.appendingPathComponent(pdfNameFromUrlArr[
    pdfNameFromUrlArr.count - 1])

// Writing the PDF file data to the Document Directory Path
do {
    _ = try pdfData.write(to: actualPath, options: .atomic) 
}catch{

    print("Pdf can't be saved")
}

// Showing the pdf file name in a label
lblPdfName.text = pdfNameFromUrlArr[pdfNameFromUrlArr.count - 1]

// URLRequest for the PDF file saved in the Document Directory folder
let urlRequest = URLRequest(url: actualPath)

webVw.isUserInteractionEnabled = true
webVw.delegate = self
webVw.loadRequest(urlRequest)

If you want to save the Pdf's in a particular folder/directory inside Main Document Directory

let resourceDocPath = (FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)).last! as URL

// The New Directory/folder name
let newPath = resourceDocPath.appendingPathComponent("QMSDocuments")

// Creating the New Directory inside Documents Directory
do {
    try FileManager.default.createDirectory(atPath: newPath.path, withIntermediateDirectories: true, attributes: nil)
} catch let error as NSError {
    NSLog("Unable to create directory \(error.debugDescription)")
}

// Split the url into a string Array by separator "/" to get the pdf name
pdfNameFromUrlArr = urlStr.components(separatedBy: "/")

// Appending to the newly created directory path with the pdf name
actualPath = newPath.appendingPathComponent(pdfNameFromUrlArr[pdfNameFromUrlArr.count - 1])

Happy Coding :)