Language
Label the language of the document, not just the page
A buyer reads a Czech product page and opens an English document without warning. That may be acceptable when the file is clearly labeled, but it is confusing when the site implies that every document has been translated.
Identify the available material
For each document, record the product, purpose, language and approved version. A language switch on the page does not establish that the linked file has an equivalent in the other language.
Keep the choice useful
A Czech supplier can show the available language options beside the document name. If only one version exists, describe it honestly. Avoid sending the reader to an unrelated file merely to make every language column look complete.
Arrange content review
Translation quality and professional terminology need the appropriate reviewer. Preserving a filename or using a translated label does not establish that the document itself was reviewed. Technical or regulated content requires its own approval.
Follow the link as a buyer
Test a product page in each supported language, open the relevant document and return to the inquiry. Check the actual destination and its label, not only the page's language attribute.
W3C's language guidance explains HTML declarations, while the document inventory supplies the real choices. We can organize that inventory within catalog work and content planning.