Sorry if this has been addressed before. I tried searching for information in the Learn to Play pdf file, but I feel information is vague enough to merit a question.

In multi-player (or more specifically Solo 2-handed play), can I put attachments from my player deck on other people's cards? The specific scenario I am thinking of is having Leadership Frodo as one deck/hand, and having Tactics Aragorn as the second deck/hand (2 different player decks). Can I have Celebrian's Stone in my Frodo deck, pay for it by Frodo, but put it on Aragorn (since it says "Attach to a hero")?

I have found the following:

Under Player Decks (on page 4): Each player has a deck that corresponds to his or her heroes. Under Phase 2: Planning (on page 9): To play a card, a player must pay the card's cost, ... Then, the card is played and placed in that player's play area. Under Placing Cards (on page 9): When a player plays an attachment card, attach it to another card that is already in play by placing it in a position so that the in-play card slightly overlaps the attachment.

If that isn't legal to do, does anyone play that way as a house rule or anything?

Yes, this is fine. The clearest statement of this is in the Rules Reference entry on attachment cards :

Quote

A player has the option to play attachments by attaching them to another player's character. When an attachment enters play attached to a character under another player's control, that player gains control of the attachment.

There is even an event in the game (which I will not say too much about to avoid spoilers) whose trigger condition is, "After another player plays an attachment on a hero you control…"

Sappidus,

Thank you for the answer and reference.

So is the site:

http://www.lotr-lcg-quest-companion.gamersdungeon.net/

the official place to get information? It doesn’t seem to be an official FFG site?

It's not an official site, but a compilation of various FFG documents—barring errors in transcription, the text is official. I link it a lot because it's the easiest way to show people things like individual Rules Reference entries. (Disclaimer: I have helped @banania in some small ways with the site.)

The original source for the above-cited text can be found here: https://images-cdn.fantasyflightgames.com/filer_public/90/19/90191e4e-a341-4379-b398-5963b7a87ebf/mec01_online_only_rules_reference_for_website.pdf