I’m up to a part in my course which is explaining about fonts, selecting the right type and also, printing processes. Anyway, I found the printing part quite difficult to understand, for example, what’s bleed? What do they mean by margins (for e.g.13mm on all sides of an advertisement). There are so many printing processes - I’d like to understand them in simple detail and also their pros and cons:
An important question: Why do designers need to learn about printing?
And what do they mean by e.g. “14–15 pt” when talking about text size?
Rather than me writing answers to all those things, you’d be better off looking up each of them. I don’t have the time to write ten pages of answers. 
As for your “important question”, designers need to learn about printing because many of the things they design are printed. In other words, they need to understand the technology and processes in order to prepare the artwork correctly for the printer and the printing process being used.
As for your question about points, that’s the unit of measurement for type sizes. From a blog post I wrote for my website two or three years ago…
"PICA — a typographical unit of print measurement that corresponds to 1/6th of an inch. Before desktop publishing and PostScript changed the rules, a pica was 0.166044 inches.
POINT — a typographic unit of print measurement that corresponds to 1/12th of a pica.
POINT SIZE — In print, type size is usually measured in points. The point size of a printed glyph corresponds to the distance between the baselines of two stacked lines of type that are set solid (with no additional leading between the lines)."
LEADING — Additional space added between lines of type. Leading (pronounced ledding) got its name from the thin strips of lead that printers placed between lines of handset type to create additional space between the lines. The term is still in use today with digital typesetting. Leading is specified in points.
If you have questions that can’t be easily answered by a Google search, feel free to ask. I (and several other people) would be happy to answer, but asking general questions whose answers could fill an entire textbook is asking a bit much.
It’s a loaded question with tonnes of answers.
There’s a saying I heard from a company called The Fold Factory run by Trish Witkowsk - and her saying is
Finishing means how it will be folded, the paper stock, the staples used, the thread if it’s threadsewn, the spine of the book, the embellishments of foil, embossing etc.
For Trish, it’s how it’s folded, that’s her game, intricate engaging folding of things to make them interactive to a user to reveal hidden messages, or unveil the story.
Finishing is how it will look and feel in your hands or see by eyes when printed and hanging in a movie theatre, or on a billboard. Will the poster be lenticular, will it have glow in the dark elements, etc.
Finishing is, how will it look when it’s in the persons hand, what paper stock, what folding, have you left enough clear space for text when the crease is applied in the printing process, does it have a gold foil, an emboss, a diecut, can it be tactile etc.
There’s many ways other than a nice design and layout it can engage an audience.
For example a very clever 3D piece - at sunset Dracula is revealed by the shadow cast by the lights.
Another example
So if a client came and said they wanted a wirobound, hard cover wrapped, with diecut tabs, and special diecut effects for intro pages, and a steel tactile page element - you need to know how to set that up in your design and in the software.
Here’s some resources and basic answers follow.
When designers prepare work for print, they need to understand a few technical things so that what they design on screen prints correctly on paper.
Bleed
Bleed is when the design extends past the edge of the page so that when the paper is trimmed, there are no white edges.
For example, if you want a photo or colour background to go right to the edge of a page, the design has to extend a few millimetres beyond the final size (usually 3 mm-5mm bleed). After printing, the printer trims the paper to the final size and removes that extra area.
There are exceptions, like a hardback cover, this has to wrap around the cover so you’re looking at 20+mm bleed so it can wrap the cover and be glued.
Without bleed, slight movement in trimming could leave thin white lines around the edges.
Margins
Margins are the safe space inside the page edge where important text and elements should stay.
If an advertisement says 13 mm margins on all sides, it means:
Text, logos, and key content should stay at least 13 mm away from the edge of the page.
This prevents them being cut off during trimming or sitting too close to the edge.
Exception is background elements that go to the edge of the page, these need to bleed, and should not contain any pertinent information.
Margins are sometimes called the safe area.
Common printing processes (simple explanation)
Offset Lithography
This is the most common professional printing method used for magazines, newspapers, books, and brochures.
Need to know: correct image resolution (typically 220-300 dpi), CMYK colour mode, RGB converting out-of-gamut to CMYK, Pantone/spot colours, halftones, bleed and trim, trapping, overprint/knockout.
How it works
Ink is transferred from a metal plate to a rubber blanket and then onto paper.
Pros
Very high print quality
Excellent for large quantities
Lower cost per unit for big print runs
Cons
Expensive to set up
Not economical for small quantities
Digital Printing
Used for short runs like flyers, posters, and small batches.
Need to know: RGB or CMYK workflow depending on printer, lower setup requirements, correct image resolution (150-300 dpi), bleed and trim, colour consistency limitations.
How it works
Similar to a laser printer. The file is printed directly from a computer with no plates.
Pros
Fast turnaround
Good for small quantities
Cheaper for short runs
Cons
Higher cost per copy for large runs
Slightly lower colour accuracy compared with offset
Screen Printing
Used for things like t-shirts, posters, signage, and packaging.
Need to know: spot colours rather than CMYK, colour separations, limited number of colours, thick ink coverage, registration alignment between screens.
How it works
Ink is pushed through a mesh screen onto the material.
Pros
Very vibrant colours
Works on many materials (fabric, plastic, wood, etc.)
Cons
Time-consuming setup
Not ideal for complex images or small runs
Flexography
Commonly used for packaging, labels, and plastic bags.
Need to know: spot colours commonly used, flexible plates, registration tolerance, trapping, substrates like plastic, film, and cardboard.
How it works
Uses flexible rubber plates that rotate on cylinders.
Pros
Very fast production
Works well on packaging materials
Cons
Lower detail quality compared with offset
Plates can be expensive
Why designers need to understand printing
Designers need to know about printing so they can design files that actually work in the real world. If they don’t understand printing, problems can happen such as:
important text being cut off
colours printing incorrectly
images printing blurry or pixelated
unwanted white edges
files being rejected by printers (costly and can miss deadlines)
Understanding printing helps designers avoid costly mistakes, communicate properly with printers, and produce professional results.
This is an important question. If you don’t understand the process by which your work will be reproduced, you will not be getting the results you expect.
About your questions about fonts i would suggest read this : https://www.adobe.com/express/learn/blog/psychology-font
