All You Need To Know About DPI

If you’re an avid photographer or work a lot with Photoshop and in printing, you know that DPI is an important value when it comes to handling images. However, it is also important when you think about PDFs. How?

PDFs can contain images, which is one of the reasons why the format became so popular for manuals, sharing books, assignments and essays, and so on. Depending on the quality of the images, the PDF is either bigger or smaller in file size – and also depending on the DPI.

Thus, the DPI plays a major role when compressing a PDF file. This is reason enough to have a look at what it actually is. 

What Is DPI?

DPI stands for “dots per inch“.

When printing an image, the DPI denotes the density of dots in the printed image. It counts the number of dots in one line of the image witch one dot having a size of 1 inch. When digitally stored, this value is rather saved as PPI (pixel per inch). A printer then converts the PPI value to DPI for the printed outcome.

When changing the DPI, or rather the PPI, in an image editing program, the image itself should retain its size, e.g. 1,000 x 1,000 pixels on a screen. However, the information sent to a printer will be different, depending on the entered value for the PPI.

There are some common values for DPI in images that are often used when talking about increasing or reducing image quality and print size:

  • 72
  • 96
  • 150
  • 300
  • 2540
  • 4000

And what does that mean for your PDF? It’s easy, the smaller the DPI of the image contained in a PDF, the smaller the file size of the PDF in the end. Hence why the PDF2Go compression tool uses presets that change the DPI of images inside a PDF.

If you want to read more about the compression presets, click here.