Is there any kind of manual or guide that would've been made up for smiths or armorers or soldiers to follow?

None that I'm aware of. Medieval arms production was a craft passed down through long apprenticeships, not an industrial process that would require/generate detailed instructions. But there are enough remaining artifacts to make fairly confident claims about their general weight range.

Plate varied tremendously with time, style, and purpose, but forty-five to fifty-five pounds is a reasonable range for a set of field plate; four to eight pounds being the helmet. Jousting armor was generally thicker and heavier.

Mail is a bit tricky, as all the (complete) surviving examples are from the 14th-15th century or later. But based on these, a mail shirt could weigh anywhere from fifteen pounds for a short-sleeved byrnie, to thirty or so for a long-sleeved hauberk with integrated mittens and coif.

With swords, you're looking at a range from about two to four pounds, with one-handed swords being around 2-3.5, and longswords (a longsword is a late medieval sword meant to be used with two hands) around 2.5-4. Exceptionally large two-handed swords like zweihanders could weigh as much as 7 or 8 pounds.

Polearms in general would range from perhaps three pounds for a light spear to eight or nine pounds for a heavy halberd. You very rarely see personal weapons much heavier than that; it seems to be about the cutoff at which it becomes unmanageable.

Shield weight would vary tremendously with size and construction, but five to twelve pounds is a pretty good range, with some classical shields being even heavier than that.