iOS PDFKit textfield form input - ios

Question

I am currently developing a iOS app which can download PDF(Have form on it) from server to iPad, then user can fill in the form on the iPad.
The problem is we need to support chinese on the field input.
Here is the field.
When I use "Quick" input method to type any character, it repeat 3 times.
When I type one more time, it repeat again.
Do anyone have issues with typing Chinese in textfield using PDFKit on iOS?
Update, Add code work
For the server-side, just a endpoint can download pdf, the pdf already added textfield on it.
On client-side, pdf is downloaded in viewDidLoad() and set into pdfView as following code.
override func viewDidLoad() {
super.viewDidLoad()
if let code = self.code {
let url = URL(string : API.pdf + "/" + code)
let loading = self.showLoading()
var request = URLRequest(url: url!)
request.httpMethod = "GET"
let task = URLSession.shared.dataTask(with: request, completionHandler: { (responseData: Data?, response: URLResponse?, error: Error?) in
DispatchQueue.main.async {
self.pdfView.document = PDFDocument(data : responseData!)
self.pdfView.scaleFactor = 1
self.pdfView.backgroundColor = UIColor.lightGray
self.pdfView.autoScales = true
loading.dismiss(animated: true, completion: nil)
}
})
task.resume()
}
}
In story board, it is just a UIView and set custom class as PDFView
Updated 2
After that, i do a simple testing.
I create a simple testing controller and load pdf with just a simple textfield annotation. Result is same.
import UIKit
import PDFKit
class PDFTestViewController : ViewController {
#IBOutlet weak var pdfView: PDFView!
override func viewDidLoad() {
super.viewDidLoad()
if let url = Bundle.main.url(forResource: "4547315264964", withExtension: "pdf"),
let doc = PDFDocument(url: url){
self.pdfView.document = doc
self.pdfView.scaleFactor = 1
}
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
}
}