Printing art (and not only art) at home is one of the easiest and most-eco friendly ways to decorate your home. But if you're not quite tech-savvy, this may prove to be quite a tricky task. I'll try to help you to navigate through the printing so you can enjoy your new home decor pieces within minutes.

First of all, there's no one size fits all type of printing guide because every printer is different and even different programs show different printing options for the same printer.
Confusing? Probably. But it doesn't have to be.

The general rule is to either know your printer really well or be prepared to print test files before printing the masterpiece printable artwork on the fancy paper you bought just for this purpose.

As I'm not a fan of waste, I'd suggest, if you opt for test printing, to print on already used paper. Maybe your old paperwork before you'll recycle it (or shred it and use it as kindling in your fireplace). Also, if you can, print any test file only in greyscale or lower the opacity (so the printing looks like a watermark and it doesn't use that much ink). If this sounds super-advanced, don't worry but it's definitely very cool to learn how to do this with your printer and save ink when printing test files.

Now, we want to minimise the number of test files, of course. So the best thing is to look at the preview. Most printing settings would give you a preview of the print. And with this, you just fiddle until you're happy with what the preview will look like. You can do various things such as centre the print, choose borderless printing (if your printer supports it - most of the newer ones do), stretch,...

About resizing/stretching: When choosing to resize always keep the ratio. Or else you'll end up with weirdly wide or narrow artwork. This may not be the worst when printing some abstract art but it won't look good for a lot of typography and also not for portraits and such.
And never resize over the actual printing size because that will cause pixelisation - the printed art won't be as crisp and clear, it would be fuzzy without well-defined edges. Tiny oversizing is usually ok if you have artwork with high DPI but don't go too much over if you want to keep the best quality.

To make sure your print will come out ok, check your paper size, see whether your chosen paper fits the artwork specifications and keep an eye on the preview in the printing settings. Usually, there's some option to print to its original size - you can check that to see whether the original fits the paper size or if it's tiny or extremely large. Large is ok, you can choose an option "fit to paper" (keep ratio). If the original looks tiny, you may want to choose a smaller paper size to print on because if you fit this one to the current paper, we'll back to the fuzzy, not well-defined printing result.

A word about DPI - this mostly applies for image files (JPG, PNG,...), not PDF - but the size will matter there too if the artwork in PDF isn't actually vectorised. When artwork is properly vectorised, you can scale to almost any size and the print will be still crisp. But not every artwork could be or is suitable for vectorisation, very often printable art is a raster image and DPI matters (or size of the print in general).
A good DPI for printing is 300 (dots per inch). If an image is 3000 x 3000 pixels, set as 300 DPI, it will "want to" print as 10 x 10 inches. Here comes the preview of the original size - you'll see how the file "wants to" be printed.

Does it sound still too complicated?
Then find your favourite way and learn the steps (tailored to your printer and program that you want to open the files with).
1) open the artwork in your favourite photo viewing/editing program (or Adobe for PDF)
2) choose print to open printing settings
3) check settings:
> you may want to change to landscape or portrait
> set the original file size - how large it "wants to" be printed (adjust the paper size if needed - or be prepared to trim extra blank paper leftovers)
> set print to scale (keep ratio)
> centre the print, ideally chose borderless printing (if the printed supports it)
4) keep checking the preview and see whether you're happy with the result before printing

When printing a test file, chose greyscale in printing settings to save ink (at least the colour ink). Don't forget to change it back to colour printing for the final printing if the settings don't reset automatically.

So, did it turn out well? If you're having troubles with your printer, the quickest way to sort it is to google help forums online for the particular brand/type of your printer. You can also search for online help with your photo viewing/editing program. Unless you have your dedicated family member who acts as tech support for things like these =) Then that may be quicker and easier.