Bit confused, can you only pull 1st ed and shadowless from 1st ed wotc packs or are they available in regular packs too like unlimited holos? Because a friend brough his old binder over the other day and he had some 1st eds and doesn’t remember buying any 1st ed packs.
Does anyone know odds of various rares, appreciated.
1st Edition cards only come from 1st Edition packages. They were specially marked skus. Or, in very very uncommon circumstances, in shadowless skus assembled on the cusp of the change.
I am assuming your friend was a child when Pokémon originally released and probably would not have noticed either way. And they probably would not remember either.
Many casual collectors do not know what 1st Edition cards even are and go back to their collections and discover they had them.
Generally 1st edition cards can only be pulled from 1st edition packs. Shadowless can be pulled from shadowless packs and theme decks. I think there are some very rare cases where 1st edition common or uncommon cards appear in shadowless packs.
edit: as for odds in older packs, it was simply 1 in every 3 packs to pull a holo.
Thanks for clarifying, yeah he was a kid, weird, he has a lot of 1st ed and shadowless, maybe he won them and nobody knew much back then, unelss 1st eds were easily available in stores, I think he only bought boosters, 1st ed packs so expensive on ebay dang 
1st Edition cards for each vintage set were, for a period of time, the only ones available. If you went in to a store to buy Pokémon cards around the time they released, you got 1st Edition cards.
In 2010 I found a hobby shop with back stock that still had 1st Edition cards for Jungle, Fossil, and Rocket. Only a handful total, but they were still there.
1st Edition cards were only hard to buy after their designated window had ended. They were not hard to buy at the launch of each set - they were the only prints that existed.
ok that explains it then, he was way into it, bought everything at launch 1999 and 2000.
like others have said 1st edition cards only came in 1st edition packs. base set there were so many variations of shadowless boxes you can pull 1st edition cards in them. I myself opened a shadowless box in like 2009 and my box had the weird thing of last 3 cards were always 1st edition