Update pdfc.md

Author: kyle-ds

indepth/features/pdfc.md

@@ -16,17 +16,15 @@ Color clustering uses operates using the RGB value of each pixel in the image to
 > This feature is only available for color or gray-scale images and requires a PDF Compressor module license.
 
 ## How to achieve high-quality compression
-
-For images which have the following attributes:
+### Select sharp simple images
+For best file fidelity post compression, please images that have the following attributes:
 
 - High contrast,
 - Less color variety,
 - Concentrated distribution of similar colors,
 - With low complexity graphics,
 
-the compression effect is good.
-
-## Things to keep in mind
+### Things to keep in mind
 
 - If the contrast between the text in the picture and the background is not high, and the weight of the text is not heavy, text may be incomplete or thin after compression.
 - If the source image contains complex graphics, the quality of the resulting compressed graphics may deteriorate.