Adding an image as a watermark or a stamp on a PDF requires only a few lines of code using Debenu Quick PDF Library. Here’s some C# sample code:

/* Add an image watermark or stamp to an existing PDF document */
 
// Load a sample file from disk. We'll place the image
// onto this file.
 
DPL.LoadFromFile("filename.pdf", "");
 
// Select page 1 to watermark
 
DPL.SelectPage(1);
 
// Load your image into memory
 
DPL.AddImageFromFile("myImage.png", 0);
 
// Get width and height of the image
 
int lWidth = DPL.ImageWidth();
int lHeight = DPL.ImageHeight(); 
 
// Draw the image onto the page using the specified width/height
 
DPL.DrawImage(250, 450, lWidth, lHeight);  
 
// Save the updated file to the output folder
 
DPL.SaveToFile("filename_watermarked.pdf");

// Load a sample file from disk. We'll place the image
// onto this file.

DPL.LoadFromFile("filename.pdf", "");

// Select page 1 to watermark

DPL.SelectPage(1);

// Load your image into memory

DPL.AddImageFromFile("myImage.png", 0);

// Get width and height of the image

int lWidth = DPL.ImageWidth();
int lHeight = DPL.ImageHeight();

// Draw the image onto the page using the specified width/height

DPL.DrawImage(250, 450, lWidth, lHeight);

// Save the updated file to the output folder

DPL.SaveToFile("filename_watermarked.pdf");