Supposing they just need to be printed (the size seems so.) We may later look for an electronics form (e.g. concatenate them to one PDF-file as an handout.)
You see, you need to fit a rectangle into a rectangle, which better should both have the same aspect ratio.
The outmost rectangle is your sheet of paper, the inner one your picture, while the margin, the not printed area between picture and paper's edges, have to be the same width at all four sides - not too narrow, not too wide - to get a good impression.
This margin consists in fact of two kind of margins: The margin you add/adjust to your picture by resizing it, and the technically margin the printer/plotter produces, which alas is not only unavoidable, but also unequal.
(Almost) every real printer/plotter always delivers a technically unavoidable margin - an area of paper not printable. Mostly top and bottom margins are narrow, while left and right margins are significantly broader. So you need to do some calculations (a + b, duh!) to know how much margin you need to add, to get the right amount of margin. For that you need of course to know the margin the printer produces. This you can get either from the technical documentation of the according printer/plotter, or print a full sided testpage, and just measure it.
That's what you always do on any printjob:
Always do a single page test print, before your start the whole print job. (And on this job you will do some until the result will fit your expectations - that's why I take my time to give you some of my experiences.
)
Anyway it's almost certain you need to cut at least two sides of the paper afterwards to make the paper fit the printed image. (Not with scissors, of course; those produce ugly edges.)
Anyway I recommend to avoid any background patterns/graphics/watermarks, at least for the printed version. Those produce lots of trouble, and at the end only lower the quality of the printed matters, only.
So, now to the main, and maybe only point you can adjust: The resizing of the picture.
There are two ways: Keeping the aspect ratio, or not keeping it.
You see resizing a picture by 50% produces a picture half the size while keeping the aspect ratio.
Resizing a 4000 x 3000 pixels or a 40cm x 30cm picture to 20m x 12 cm, or 2000 x 1200 pixels makes it even smaller than 50%, but the aspect ratio is not kept, which means the picture will be distorted.
Depending on the kind of picture a bit distortion (app. ~ 5..10%) may not stick out, and is tolerated by the viewer. So that gives you a bit clearance for adusting the picture's size to fit into the margin.
If no distortion is allowed at all (any graphs must stay true to scale), then you have to keep the aspect ratio.
Supposing all pictures you need to print have the same size, the same aspect ratio, same resolution, you pick one (at best the one with most smallest details (graphics/fonts) later need to be distinguished.)
Load it into your favorite graphics program (e.g. Gimp), and see what size it currently is (of course, you work on copies of the files - needless to say) and how much percentage you need to resize it to fit the targeted paper size (percentage, pixels, better mm, with keeping aspect ratio, or not.)
You can do it all in Gimp (or another painting program capable for the job), but depending on the amount of pictures that's an effort can be spared by using a computer a computer is for: automate it. If not done already install ImageMagick.
This way you can use its tools for doing the jobs needed to be done finally for all pictures automatically with a small script: potentially turn them by 90° to fit landscape onto portrait paper sheet, resize them to the new format you figured out manually once, and convert them into a file format you can deliver to your printer (Postscript, PDF, whatever the printer/plotter wants.)
You see, you need to fit a rectangle into a rectangle, which better should both have the same aspect ratio.
The outmost rectangle is your sheet of paper, the inner one your picture, while the margin, the not printed area between picture and paper's edges, have to be the same width at all four sides - not too narrow, not too wide - to get a good impression.
This margin consists in fact of two kind of margins: The margin you add/adjust to your picture by resizing it, and the technically margin the printer/plotter produces, which alas is not only unavoidable, but also unequal.
(Almost) every real printer/plotter always delivers a technically unavoidable margin - an area of paper not printable. Mostly top and bottom margins are narrow, while left and right margins are significantly broader. So you need to do some calculations (a + b, duh!) to know how much margin you need to add, to get the right amount of margin. For that you need of course to know the margin the printer produces. This you can get either from the technical documentation of the according printer/plotter, or print a full sided testpage, and just measure it.
That's what you always do on any printjob:
Always do a single page test print, before your start the whole print job. (And on this job you will do some until the result will fit your expectations - that's why I take my time to give you some of my experiences.
)Anyway it's almost certain you need to cut at least two sides of the paper afterwards to make the paper fit the printed image. (Not with scissors, of course; those produce ugly edges.)
Anyway I recommend to avoid any background patterns/graphics/watermarks, at least for the printed version. Those produce lots of trouble, and at the end only lower the quality of the printed matters, only.
So, now to the main, and maybe only point you can adjust: The resizing of the picture.
There are two ways: Keeping the aspect ratio, or not keeping it.
You see resizing a picture by 50% produces a picture half the size while keeping the aspect ratio.
Resizing a 4000 x 3000 pixels or a 40cm x 30cm picture to 20m x 12 cm, or 2000 x 1200 pixels makes it even smaller than 50%, but the aspect ratio is not kept, which means the picture will be distorted.
Depending on the kind of picture a bit distortion (app. ~ 5..10%) may not stick out, and is tolerated by the viewer. So that gives you a bit clearance for adusting the picture's size to fit into the margin.
If no distortion is allowed at all (any graphs must stay true to scale), then you have to keep the aspect ratio.
Supposing all pictures you need to print have the same size, the same aspect ratio, same resolution, you pick one (at best the one with most smallest details (graphics/fonts) later need to be distinguished.)
Load it into your favorite graphics program (e.g. Gimp), and see what size it currently is (of course, you work on copies of the files - needless to say) and how much percentage you need to resize it to fit the targeted paper size (percentage, pixels, better mm, with keeping aspect ratio, or not.)
You can do it all in Gimp (or another painting program capable for the job), but depending on the amount of pictures that's an effort can be spared by using a computer a computer is for: automate it. If not done already install ImageMagick.
This way you can use its tools for doing the jobs needed to be done finally for all pictures automatically with a small script: potentially turn them by 90° to fit landscape onto portrait paper sheet, resize them to the new format you figured out manually once, and convert them into a file format you can deliver to your printer (Postscript, PDF, whatever the printer/plotter wants.)
