Well, this is either a minefield or a can of worms. Or trying to close a can of worms while wading towards a minefield through a swampful of alligators.
If you are printing via a printing lab and ask them to adjust the brightness, they can do so but there is no way of knowing what they will think is the right brightness. They may also decide to alter the colours.
Printer drivers (i.e. the software that makes a printer function at all on a computer) have image "enhancement" features. Those alter the contrast, brightness, colours and sharpness to whatever the author of the driver thought was desirable. That may or may not be something like what you intended. I recommend switching such features off.
Whether or not the image after your "final PP" will come out how you meant it to will depend on how you did the PP. If you have calibrated and profiled your monitor with a calibration device, and set up a colour managed image editor (like photoshop) to correctly use the profiles, then you should be nearly OK.
I say "nearly OK" because, prints often come out darker than monitors, even in colour managed workflows, for lots of rather complicated reasons. That is why the best way is to use a fully colour-managed workflow AND make adjustments to it based on the experience of actually comparing the prints with your monitor display.
In order to do that, I prefer a printing service that makes absolutely no alterations. I want them to print what I give them. If I don't like what comes back, I will alter my file and re-submit it.
Your Island Guide publisher will employ print experts and have a very good idea of how bright/dark/colourful they like their images to be. And they know the Island. If they came out how you wanted, that is good.
After all, I could take one of your files and alter it so as to print how I would like. But it would not be your preferences then - it would be mine - especially as I have no way of knowing what you see on your monitor.
I suggest you ask your printer to print just one of your files without altering it at all and see what comes back. If it is good, you have no problem. If it is too dark. light, green, blue or whatever, then tell them. Then you can ask them if they can fix whatever was wrong for you or do it yourself. But at least you would know what needed fixing and in what direction.
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I have a home on pbase
http://www.pbase.com/claypaws/
If you have the time to look
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