Hi
I hope i can help with this, there isn't a one sentence answer i am afraid.
When you work on screen and print comes out dark there are various possible reasons.
Colour management can definitely help you, so you're on the right forum.
Note - below I'll mention colour spaces and working spaces, both are defined by ICC profiles.
No 1 issue
This is the most common, your screen is not properly calibrated and profiled (this process is carried out by software working with a measurement instrument like a Datacolor Spyder or i1display pro - those are screen sensors which work with the software to set your screen up right.
Out of the box - many display screens are way too bright. This misleads a user into making dark images, they then look good on only your very bright screen - not in print.
No 2 issue
How are you working, how are you printing?
If you are making a file in Photoshop, it's likely you should do your work using one of the installed (device independent) working spaces, like Adobe RGB or sRGB. Same goes for Indesign and Illustrator, although do note that many working in those 2 applications work in a CMYK colourspace, that is a colourspace tailored for a specific printer.
A CMYK colour space is ALWAYS tailored for a specific printer.
See what I wrote there: A SPECIFIC PRINTER.
Whilst working spaces (e.g. sRGB) are device independent, CMYK colour spaces are device specific.
if you want to work to CMYK you HAVE TO ask the printer what CMYK profile to use.
There are freely available standards based CMYK print ICC profiles for magazines, reports etc. from GRACoL and eci.org. Some a=re included in Adobe applications but you have to choose the right one. And the printer is the guy to tell you that.
Maybe read up a bit here about what ICC profiles are, what they do and how they can help you:
color management / colormanagement : about icc colour profiles
and about screen calibration and profiling here
display screen colour management, calibration and profiling | colourmanagement.net
I hope this helps you
if so, please do mark my reply as "helpful" and if you're OK now, please mark it as "correct" below, so others who have similar issues can see the solution
thanks
neil barstow, colourmanagement