I am generating files for documentation of new PCB release. Previous were 2021.04.
I have done minor changes at schematic.
I plot schematic to PDF (to be fast opened whenever I need it) and to SVG (to be easily inserted in LibreOffice Writer document).
PDF was 109k and now is 300k (431k with Generate property popups switched on).
SVG was 669k and now is 2,22M.
Do you know why just simple graphic representation of schematic need more and more bytes?
Do you mean you have plotted with older and newer KiCad versions?
Maybe because plotting doesn’t make just “simple graphic representation”. It has other features like searchable text strings and links between items. Open a (new) plotted pdf schematic with a full-featured pdf reader to see what I mean.
Of course. I compare today generated files with old ones.
In 2021 KiCad was V5, I think.
I use schematic SVG output only to insert it into LibreOffice writer documentation to have whole documentation in one file to be printed. And on paper all potential possibilities don’t want to act 
In pdf I switched off ‘Generate popups’ (what I found today) as it looks that it practically gives nothing very useful. But even it is switched off the file is still 3 times bigger because there probably are many things inserted I just know nothing about them. In my opinion if it is so then we should have another checkbox to switch it off. I open any old schematic (in pdf) may be once or twice a year.
Acrobat Reader in Help-About says 2024.003.20180 version. I suppose it is full-featured reader.
I remember times when I was designing PCB using program that was distributed at 4 360kB floppies and I managed to run it at IBM-XT having no HDD (only 2 floppy-disk drives) and 640k RAM.
This is probably why I’m a bit crazy and I don’t like my backup growing and growing (and it seems to me that completely unnecessarily).
I just think - the bigger my backup the more time I loose on it. Even if these are few extra seconds a day they accumulate over the years.
By best guess is it has something to do with the schematic file format change in KiCad V6. I like the human readable S-expressions, and embedding of all used library symbols which made an end to the [??] symbols from V5 and earlier, but maybe they also went a bit over the top with even giving wire segments and junction dots their own UUID (which are pretty long strings). Those things don’t necessarily have to trickle over into PDF or SVG output, but I guess some of it does.
Computer speed and disk space is still getting cheaper and faster at a quicker rate then my storage needs. I did an $ apt update today and it was over a GiBi download, the following $ apt upgrade was another 1.2GiBi. and that did take just long enough to become slightly annoying, Maybe one or two minutes.
12TB HDD’s are now fairly common and with a cost of EUR250, that is close to EUR25 per TB. 10Gbps Ethernet has kept on being relatively expensive for a long time (and still is).
Every now and then I thought of either building or buying a NAS and getting into a more systematic approach to backups. My current method is with a few HDD’s in silicone protection sleeves that I put directly on a SATA port. Recently I have abandoned that Idea. I’m going to semi permanently put those extra HDD’s in my PC, and then switch the SATA power with a few relays. (Data is always connected). It’s very simple to push a button to turn a relay on, and then it just stays on until the PC is turned off. Alternatively you can throw a uC in the mix. Turning them only on when needed reduces wear, and makes them inaccessible to any sort of malware and mayhem short of burglary and fires and such. Only off-site backups help for those.
For short term (daily) backups you can put an extra M.2 SSD in your PC. 500GB for EUR 40. Not even worth fussing about. It’s plenty for backing up your own work. I only don’t trust SSD’s for long term storage.
Something about 5 (or more) years ago I got from my friends birthday gift - 1TB external USB HDD. I was vary happy to get it, but during these 5 years I didn’t had a need to even once connect it to any PC . So till now its only function is to make me happy having it. It has a special cover…
I suggest you start using it either for backups or for moving files around. If that one is precious to you, or you need a bigger one for your backups, an external 2.5" disk of 1TB costs around EUR60 these days (much less then 5 years ago) but 4TB (EUR130 for 2.5") is relatively cheaper. I don’t know what your current backup strategy is. I hope you don’t simply rely on a single PC. Best I know, HDD’s are the most common backup media these days. They do have a mechanical disadvantage over solid state memory, but that is offset by both their price, and their longer data life. You can have multiple HDD’s and data does not leak (as quickly) as when you put an SSD in a drawer (or a vault, whatever).
But it’s all terribly off topic for this KiCad forum. It’s unlikely your files will get (much) smaller, and it’s probably better to grow with the times and up your storage speed and size.
Meh, what a totally unsurprising situation. 
. Now if you had written Files smaller and smaller that would be newsworthy. Deal with it. 
The small backpack (I take to work) has an easily detachable key clip and I have a bunch of pendrives there instead of keys. This way one copy of my backup is always with me.
Pendrives are easier to use than USB HDD.
When my daily backup files reach about 10MB I make big backup (about 200M) and then my daily backups begin with being about 200-500k and rising.
Big backup I do 4…6 times a year.
All my backups since 2004 takes half of 32G pendrive now.
The KiCad roadmap says that 3D model will be (optionally?) included. These will make massive pcb files
It’s scary to be afraid.