title: Increase DPI in photoshop
body: <p>I'm totally new to photoshop and I need to do something I don't really know how.</p>
  
  <p>I got a picture with 100 dpi. We want that picture to be printed on a poster. I need to increase that 100 dpi to 300 dpi.</p>
  
  <p>In photoshop, I went to Image/Image size. I uncheked "Resample Image", switched 100 pixel/inches to 300, but the document size has decreased. The thing is that I do not want to change the poster size. Is the "document size" the same as the poster size? If yes, what should I do to conserve the actual size with increasing from 100dpi to 300dpi? Is growing the image size from 3x is the better solution?</p>
  
  <p>Thanks.</p>