how can a password-protected PDF file be opened programmatically?
Solution 1
To open a password protected PDF you will need to develop at least a PDF parser, decryptor and generator. I wouldn't recommend to do that, though. It's nowhere near an easy task to accomplish.
With help of a PDF library everything is much simpler. You might want to try Docotic.Pdf library for the task (disclaimer: I work for the vendor of the library).
Here is a sample for you task:
public static void unprotectPdf(string input, string output)
{
bool passwordProtected = PdfDocument.IsPasswordProtected(input);
if (passwordProtected)
{
string password = null; // retrieve the password somehow
using (PdfDocument doc = new PdfDocument(input, password))
{
// clear both passwords in order
// to produce unprotected document
doc.OwnerPassword = "";
doc.UserPassword = "";
doc.Save(output);
}
}
else
{
// no decryption is required
File.Copy(input, output, true);
}
}
Docotic.Pdf can also extract text (formatted or not) from PDFs. It might be useful for indexing (I guess it's what you are up to because you mentioned Adobe IFilter)
Solution 2
If you use SpirePDF then you can get images of the pages out of an ecrypted PDF like this:
using System;
using System.Drawing;
using Spire.Pdf;
namespace PDFDecrypt
{
class Decrypt
{
static void Main(string[] args)
{
//Create Document
String encryptedPdf = @"D:\work\My Documents\Encryption.pdf";
PdfDocument doc = new PdfDocument(encryptedPdf, "123456");
//Extract Image
Image image = doc.Pages[0].ImagesInfo[0].Image;
doc.Close();
//Save
image.Save("EmployeeInfo.png", System.Drawing.Imaging.ImageFormat.Png);
//Launch
System.Diagnostics.Process.Start("EmployeeInfo.png");
}
}
}
John Smith
Updated on June 05, 2022Comments
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John Smith almost 2 years
The Adobe IFilter doesn't provide a mechanism to supply a password to open a password-protected PDF file, so it cannot be used to open password-protected files.
I was wondering, is there a relatively straightforward way to programmatically retrieve the actual encrypted data inside the PDF file, decrypt it using a standard cryptography API, and then build a new PDF file with the decrypted data?