Space saving tip: reduce pdf size

SaskiaP

Because I'm running out of my 2GB of storage space, I scrutinized my storage for space gobbling files. I noticed that a lot of the PDFs in my database were pretty huge, without a very good reason.

Acrobat Pro has the option to reduce the file size (in version XI it is under File, Save as Other, Reduced Size PDF) and it does that very well. You can run it on multiple files at the same time and save it under the same name as the file you have open, so you don't have to tell Zotero that it should attach to a different file instead.

With some fiddling and scripting, I ran that on all 1500+ pdfs in my database and freed up approximately 250Mb. I thought that was notable.
The most spectacular win was on an 11 page paper that went from a whopping 67Mb to 210 Kb with no observable loss of quality (https://www.ncbi.nlm.nih.gov/pubmed/27698620 if you want to see for yourself). I guess publishers don't really pay attention to how large a file gets.

The only thing now is to get Zotero to sync the online library with the new, reduced size pdf's, because the online versions are still the large ones. I waited a bit to see if it would notice, but it doesn't, so here's the use for the option under preferences, sync, reset, restore to online library.

dstillman

Don't use Restore to Online Library for this — that's way overkill and can cause other problems. Zotero will sync the files up as long as their modification times change.

SaskiaP

I waited for that a couple of days, but it didn't. What triggers the syncing, exactly?

Zotero doesn't check the entire repository of attachments for changes every time it runs, of course: that would slow it down a lot. I thought that, maybe, the option under advanced preferences to check database integrity might, but that didn't prompt syncing either.

Now that I ran the reset of the online library, I just checked the status of my online storage, and it dropped from 87% usage to 53%. Apparently, there was more unsynced stuff lingering in the online storage than just the large versions of the PDFs.

I haven't run into any problems, yet, after the restore of the online library, so for now, I am just happy with having plenty of space available online again :)

dstillman

Zotero doesn't check the entire repository of attachments for changes every time it runs, of course: that would slow it down a lot.

It checks files for changes 1) in the startup auto-sync, 2) on an auto-sync after at least 3 hours from the last one, and 3) when you click the sync button manually.

But as I say, what matters is that the modification times of the files change — that's what causes the files to be uploaded.

Lynx_TWO

Not to resurrect an old thread, but if you don't have Adobe Pro (or even if you do) there's a free program called File Optimizer that can losslessly reduce PDF sizes, especially if they are using an older PDF version. I optimized my entire database and some files were reduced by as much as 41% of the original size.

Here's the link: https://nikkhokkho.sourceforge.io/static.php?page=FileOptimizer

Scroll around 25% down on the page, and you'll see the link to the installer. This program is a beast that can losslessly (or lossily, choose your setting wisely!) optimize hundreds of different file types in addition to PDFs