PStill Use Case: PDF/A Generation on the command line:

Applies to: ALL VERSIONS 1.90.xx and newer.

Assumes output will be sRGB. Input may be in any color space and will be converted to sRGB.
 
To generate PDF/A-1b from any supported source (PDF, EPS, PS. PNG, JPEG, TIFF, etc.) use these options:

-v -M defaultrgb -d 400/200/300
 -m "XPDFA=" 
 -M cmykcolorprofile=/path/to/optionalCMYKprofile.icc -o output.pdf input.pdf

The CMYK profile provided will be used for any color conversion from CMYK to the
sRGB output color space. It should match the CMYK space of the source. If 
you do not supply it, the colors will be converted generically.

PStill will use the target color profile automatically from its profile folder for RGB, likewise
it will set the intent to "sRGB IEC61966-2.1".

Option -M cmykprofile=... is optional, it will however generate better looking (exact colors)
results from CMYK PDF source. For RGB PDF sources it has no effect.
 
Images will be downsampled to 200 dpi (color/gray images) and 300 dpi (monochrome). This is
also optional and can be controled by the -d ... option.