Did PIE put the adjective behind the noun (like Romance languages usually do) or before the noun (like Germanic languages)?
Here are some reconstructed phrases in PIE. It seems, the adjective could go both before and after the noun. Examples:
- Adjective before
h₁ōḱéwes h₁éḱwoes "swift horses"
dus menes "bad mind" (> "bandit, enemy")
dus dius "bad sky"
- Adjective after
ḱléwos wéru "wide fame"
ḱléwos meǵh₂ "big fame"
ḱléwos ń̥dʰgʷʰitom "imperishable fame"
So it seems,
The adjective dus "bad" was always put before the noun, but it can be interpreted as the prefix of the noun rather than a separate word. The same with the adjective h₁su "good". Again, it may be seen as a prefix.
There were other prefixes that are similar to adjectives, adverbs or prepositions, such as sm(i)-, twi-, tri- (one, two, three), those pointing location etc, such as pri-, peri-, h₂nti-, h₂ntbhi-, proti- etc.
Possessive participles were put before the noun, as in
sh₂uens kʷekʷlos "Sun's wheel"
dems potis "house master"
Other adjectives, possibly could go the both ways, or depending on context.
PIE had a rich inflection system, as is echoed in the oldest attested daughter languages. Owing to this, if adjective and noun were each appropriately declined, the order could be either way.
As to the actual order, there is not enough evidence to support an absolute trend either way in PIE.
Remember that word order is more important in modern Germanic and Romance languages due to a simplified inflection system. Some other Indo-European languages, such as Marathi, are still relatively free in their word order in general.