Etsy Digital Downloads: A File Checklist Before You Publish

The limits
An Etsy listing for a digital item accepts up to 5 files, each up to 20 MB. Check the current rules on Etsy before you publish, since they can change.
Count and weigh your files
Add up files and their sizes first. If you have 40 files, they must be grouped into ZIPs. If one file is larger than 20 MB, split it into parts and include a short guide on how to join them, or deliver a PDF with a download link.

Etsy File Fit checks files against Etsy's 5-file / 20 MB rules. Product page
Group by what the buyer needs
Sort by format (PDF, JPG, PNG) or by paper size (A4, Letter, A3), not alphabetically. A buyer who wants only one size should not have to open every folder.

Etsy Bundle Builder sorts product files into ZIPs by format or paper size. Product page
Add a START HERE page
A one-page PDF telling the buyer what is inside, which file to open, and how to print or edit it prevents most messages asking where the file is.
Print sizes: exact pixels per ratio
Common print ratios are 2:3, 3:4, 4:5, 5:7 and 11:14, plus the A series. One artwork cannot fill all of them without cropping, so export each ratio at its exact pixel size and label it clearly.

Etsy Print Sizes exports one artwork at the exact pixels of each print ratio. Product page
Match the listing text to the files
If the description promises 5 sizes in JPG and PDF, the ZIP must contain exactly that. Compare the promised sizes, formats and file counts against what you uploaded; missing or extra files cause bad reviews.

Etsy Listing Match compares the listing text with the files you uploaded. Product page
Updating an older product
When you release a new edition, compare the old and new package. Old files left in the new ZIP confuse buyers. Write a short changelog for people who already bought it.

Update Pack Builder compares an old and a new package and builds a clean ZIP. Product page
Offline browser tools for this: Etsy File Fit, Etsy Bundle Builder, Etsy Print Sizes, Etsy Listing Match and Update Pack Builder.
They run offline in the browser, so your files are not uploaded anywhere. All products and prices: https://asecrier.gumroad.com
A PDF version of this checklist is on Scribd.