Getting ready for print Margins bleed etc.


Hi guys I'm new here but I actively follow the forum.

I'm a 3D artist turn graphic designer and I have over 2 years experience working for clients however I am not a graphic designer by education. I am self taught and unfortunately this means I have skipped a few steps along the way, anywho without digressing more.

I have worked with print and bleed a lot and bluffed my way through it, I have read countless FAQs and spoke to many print technicians however I still don't quite understand it.

I am currently working with a client to produce a catalog however when you produce a A4 Catalog where does the print/bleed/margins begin or end. I notice If i produce an A4 document which fills the 297 x 210 (UK A4) in Illustrator or Indesign it asks me to scale (90%) when printing. Should I be producing the artwork to 280 x 189 allowing for 2-3mm bleed all around essentially leaving 11mm x 15mm of white space? Or should my document be 280mm x 189mm. Is there a standard?
If you want your final size to be A4 then you need to add bleed outside this area. If you look at Indesign then you can set bleed when you set up your pages, (at the bottom of the set-up page 'Bleed and slug' - don't worry about slugs). Then when you make your pdf you need to click in the menu 'Marks and bleeds' and then check the 'use document bleed box'. I always set a bleed on every page regardless of whether I am using bleed or not. Set a bleed of 3mm all round.

If you print on an A4 printer you will not be able to print a full page showing bleed and crops unless you reduce it!

Take a look at Bleed & Crops | What they are and how to use them in print
I understand the bleed, its more to do with scaling, when I print a PDF it asks me to scale it (on a standard printer), thank you for getting back intouch.
Obviously an A4 printer won't print a full A4 with bleed. If you are going to print it then keep it A4 + bleed.
The documents I create are due to be mass produced as a handout with our products however at present they are available on request so they are generally printed on a domestic printer, would you suggest using margins so that important information isn't cropped out, or would you use the whole document and allow for scaling?
Kate (who is the font of all knowledge) is completely correct. So if you are going to produce an A4 to be printed commercially then, yes, you will need bleed. If you are producing handouts to be printed in-house on a regular printer then just output as an A4 but do not include bleed and leave the page as A4. All that will happen is when you go to print them yourself you will open them via Acrobat / Adobe Reader (whichever you have) and you select "shrink to fit" and your printer will print covering as much of the page as it is capable of, automatically scaling to fit.
Thanks Kate and spottypenguin. Just over analysing, I wasn't sure if scale was more important and if I should compensate for this.