During my engineering training, several decades ago, we learnt that A4 is 297x210mm and accordingly A5 is 210x148,5mm.
Today an intern showed me a template she is making and I noticed that she had only created pages of 210x148mm. Turns out that Scribus had pre-sets called A5 with that size. My eyes did not like the "surplus" strip of 1mm when two pages are shown on one sheet-A4 (even on the screen it looks wrong to me).
Next I took my intern to Wikipedia and was surprised that indeed there is a mention in ISO 216 of "rounded to the nearest millimetre". So A5 is listed as 148x210mm.
Now our intern is preparing a series of 33 childrens' activities sheets which will be produced in four different ways:
initial drafts on folded A4-sheets from our office laser printer
folded A4 sheets, giving four pages A5 each, mass-printed b/w by offset for each child to have and work in
sets of A2 posters in full colour for the teachers on cardstock; one for each page, so the activities can be explained to the class
- A5 PDF-Documents of four pages in colour for online distribution to kids/parents
As we are planning for mixed production from the same Scribus-file, including blow-ups to A2, and also want to take our documents to a professional print-shop, I do not want to mess up the page-size from the start.
This educational project is meant for West Africa and will take hundreds of hours of creating the activities and the layouts, so this is why I am asking for your help. Our budget is limited but we want to do proper files and respect norms.
What do other users do? Force Scribus or InDesign to a page width of 148,500mm when two pages are printed unto a sheet of A4 size? Or really set your DTP program to a page-width of 148mm and accept that two pages on an A4 sheet will end up further to one side? Is there a setting somewhere, where we can precisely place our A5 pages on the A4 paper-sheets (for example to allow generous space for the center-fold)?
Update: I have researched prizes at online print-shops and as an indirect benefit I looked over their specs or instructions: Seems that in real life (Germany) they prefer an A5 document in 148,0 x 210,0 mm (plus bleed, which is 3mm all round for the digital print-shop which will get our order).