Prevent copy and paste of PDF content - iOS devices

Question

Is there a way I could prevent the user from copying the content of a PDF file on iOS devices?

To detail a bit the background of this query, I have an app that is downloading a PDF and displaying it in the browser. The file is provided by a .NET Core web api and the client that it's serving the file is developed in Angular.

At the API level I am using iTextSharp to encrypt and set permissions for it (just printing permission). This works without any issues on desktop, but not on iOS devices.

If anyone could help me, I would be grateful.

UPDATE

.NET Core encryption method

public byte[] EncryptPdf(byte[] bytes, string encryptionKey)
        {
            using (var ms = new MemoryStream())
            {
                using (var reader = new PdfReader(bytes))
                using (var stamper = new PdfStamper(reader, ms))
                {
                    stamper.SetEncryption(null, Encoding.ASCII.GetBytes(encryptionKey),
                        PdfWriter.ALLOW_PRINTING, PdfWriter.ENCRYPTION_AES_128);
                    stamper.Close();
                }
                return ms.ToArray();
            }
        }

Angular snippet for handling the blob

downloadFile(data: any) {
    var windowUrl = window.URL || (window as any).webkitURL;
    if (navigator.msSaveOrOpenBlob) {
      navigator.msSaveOrOpenBlob(data.body, this.getFileName(data));
      return;
    } else if (navigator.userAgent.match(/iPad/i) || navigator.userAgent.match(/iPhone/i)) {
      const url = windowUrl.createObjectURL(data.body);
      window.location.href = url;
      return;
    }
    saveAs(data.body, this.getFileName(data));
  }