This rule excludes a single object from item distribution. This can be a Actor Reference, ActorBase, Race, Keyword, Faction, CombatStyle, or Class.

1|4|<FORMID,PLUGINNAME><FORMID2,PLUGINNAME2>...
Example: 1|4|<2B74,Dawnguard.esm>- Excludes Serana

NPCs that are excluded due to a Faction, but have a distribution directly assigned to them (Actor or Actorbase), are not excluded. Only direct Actor/Actorbase and plugin excluding can exclude such NPCs.

This rule excludes a single object from item distribution if it does not have a dedicated rule. It can use the same objects as above.
Using this rule, makes sure that an NPC does not use the default rule.

1|5|<FORMID,PLUGINNAME><FORMID2,PLUGINNAME2>...
Example: 1|5|<2B74,Dawnguard.esm>- Excludes Serana if she does not have any rule

This rule excludes all NPCs from a plugin. It does not affect Factions, Keywords, etc. in this plugin.
This may not work for all dynamic NPCs that are dynamically spawned, as they cannot always be associated with the mod that spawns them.

1|17|PLUGINNAME
Example: 1|17|Skyrim.esm - Excludes all NPCs from Skyrim.esm


This rule excludes a single item from being distributed from any NPCs. NPCs will not use excluded items, even if some other mod distributes them.

1|4|<FORMID,PLUGINNAME><FORMID2,PLUGINNAME2>...
Example: 1|4|<18EF3,Dawnguard.esm>   - Excludes Potion of Blood


This rule excludes all items from a single mod from being distributed.

1|9|PLUGINNAME
Example: 1|9|Skyrim.esm   - Excludes all potions, poisons, and food from Skyrim.esm

This rule excludes all items in the game that have a specific effect.

1|16|Effect
Example: 1|16|40000000000     - Excludes all items with the ReflectDamage effect

Effect is a hexadecimal ID which you can find in the documentation on the right side of the table as comment.

This rule marks an item as alcoholic. If the corresponding setting is activated, the player will not use items marked as alcoholic

1|19|<FORMID,PLUGINNAME><FORMID2,PLUGINNAME2>...
Example: 1|19|<d055e,> - Marks Stros M'Kai Rum as alcoholic


This rule excludes items from being used by the player only. NPCs will use the items as normal.

1|21|<FORMDID,PLUGINNAME><FORMID2,PLUGINNAME2>...
Example: 1|21|<18EF3,Dawnguard.esm>- The player cannot use Potion of Blood


This rule declares an Actor as a boss character, which maximizes the chances for item distribution and strength of the items. 

1|3|<FORMDID,PLUGINNAME><FORMID2,PLUGINNAME2>...
Example: 1|3|<13B79,><19951,> - Declares Chief Burguk and Chief Larak as bosses


This rule modifies the strength of an actor.

1|11|RelativeStrengthAdjustment|<FORMID,PLUGINNAME><FORMID2,PLUGINNAME2>...
Example: 1|11|2|<41fb8,>  - Increases the strength rank of Captain Aldis by 2

RelativeStrengthAdjustment is a number (positive or negative)

This rule sets the strength of an item

1|10|ItemStrength|<FORMID,PLUGINNAME><FORMID2,PLUGINNAME2>...
Example: 1|10|<FF9FE,>- Declares the Elixir of Strength as Insanely strong

ItemStrength ranges from 1 to 4 (Weak = 1, Standard = 2, Potent = 3, Insane = 4)

This rule sets the AlchemyEffect that is associated with a specific magic effect

1|20|<FORMID,PLUGINNAME><FORMID2,PLUGINNAME2>...|Effect
Example: 1|20|<3AC2D,Skyrim.esm>|1- Associates the Waterbreathing Magic Effect with the Health Alchemy
  Effect. This will make the mod use items with Waterbreathing
  whenever a health effect should be applied.

Effect is a hexadecimal ID which you can find in the documentation on the right side of the table as comment.
This rule can be used to define Alchemy Effects for Magic Effects that cannot be recognized by the ActorValue they are associated with.
It can also be used to change the AlchemyEffect for Magic Effects that can be recognized by their ActorValue but should behave in a different way.
Lastly this allows to assign behaviour to items that only have script-only magic effects.

This rule whitelists single objects. (Items - potions, poisons, food, Actors, Actorbases, Races, Keywords, Factions, CombatStyles, Classes) 

1|7|<FORMID,PLUGINNAME><FORMID2,PLUGINNAME2>....
Example: 1|7|<76f17,>  - Whitelists the Falmer Blood Elixir, no scam to be seen...

Whitelisting items means they are going to be distributed to actors.
Items that are excluded cannot be whitelisted. The plugin will not tell you this, you will have to check yourself.
Whitelisting anything else means, that matching actors will receive items.
NPCs that are excluded in any way, cannot be whitelisted. If you want to debug this, use the console command nupstats on an actor.

This rule whitelists all items from one plugin.

1|12|PLUGINNAME
Example: 1|12|Dragonborn.esm   - Whitelists all items added by Dragonborn.esm

This rule whitelists all Actors from one plugin

1|18|PLUGINNAME
Example: 1|18|Dragonborn.esm- All NPCs defined in Dragonborn.esm are whitelisted and may receive
items.

And for to who ask "Why not combine rule 12 and 18?"  be said: "Just because you want to include all NPCs, it does not mean you want all the Items."

Not all followers use the base game factions, for instance "Sofia - the funny fully voiced Follower" uses its own factions that indicate when Sofia is a follower and when she does not follow the player.
This rule lets you declare such factions. An actor will be considered a follower if they are in the faction and have a faction rank >= 0.
CurrentFollowerFaction and CurrentHirelingFaction of the basegame are integrated and do not need to be declared this way.

1|13|<FORMID,PLUGINNAME>
Example: 1|13|<60480,SofiaFollower.esp>- Tells the mod that members of the SofiaFollowerFaction are active
followers

Only accepts Factions.

Sets the dosage used for single poison items. The dosage is the amount of hits the poison lasts on your weapon.

1|14|Enforce|<FORMID,PLUGINNAME><FORMID2,PLUGINNAME2>...|Dosage
Example: 1|14|1|<74A39,>|20   - Sets the dosage of Potent Paralysis Poison to 20 (#Medusa) and
  enforces it (disables other rules that define different values)

Dosage is a positive integer or "setting". The last one uses the mod setting as dosage. may be useful when overwriting Effect rules (see below).

Sets the dosage of poisons that have a specific effect.

1|15|Enforce|<Effect><Effect2>...|Dosage
Example: 1|15|0|<800001><10000000>|3  - Sets the dosage for the Health effect (1), the ResistFire
  (800000) and the Paralysis effect (10000000) to 3, without
  enforcing it.

Effect is a hexadecimal ID which you can find in the documentation on the right side of the table as comment.
You can combine multiple effects by addition:
Effect1       1
Effect24000
Total    4001
The items specific rule has a higher priority than this rule.
If a poison has multiple effects, the lowest dosage for any effect will be chosen.

Attaches an object to a distribution rule. Valid objects are Actors, Actorbases, Races, Keywords, Factions, CombatStyles and Classes. With the first having the highest priority when calculating which rule to choose.

1|2|<FORMID,PLUGINNAME><FORMID2,PLUGINNAME2>...
Example: 1|2|Adventurer|<b9982,> - Attach Jenassa to the Adventurer rule
Example: 1|2|VampiresRoyal|<3376,Dawnguard.esm> - Attach the DLC1VampireFaction to the VampiresRoyal rule

Available rules:
Adventurer, Assasins, Bandits, Caravan, CarriageDrivers, Civilians, Cultists, Dawnguard, Draugr, Dremora, EbonyWarrior, Falmer, Forsworn, 
Hunter, Mages, Nightingales, Nobles, Orcs, PenitusOculatus, Priests, Poor, Rieklings, Righteous, Scum, Thalmor, Thieves, Vampires,
VampiresRoyal, Vigilant

Distribution rules have a priority field. When multiple rules may apply to an actor, the rule with the highest priority is chosen. The rules and the priorities are defined in NPCsUsePotions_Default_NUP_DIST.ini. If you have problems apply a rule to an actor, consider using the console command nupstats on an actor in-game. It will print you all rules that could have applied to an actor and the respective rules priority. Don't expect a nice formatting though, its meant for debugging.

This rule defines the distribution rules. It include the number of items, the chances, the possible effects and everything thats important for the distribution of items. Here the new version introducted in version 3.0.0 is described. [The old rule version is still valid and fields that are not present are set to 0.]

2|1|RuleIdentifier|RulePrio|MaxPotions|Potion1Chance|Potion2Chance|Potion3Chance|Potion4Chance|PotionAddChance|PotionsTierAdjust|MaxFortify|Fortify1Chance|Fortify2Chance|Fortify3Chance|Fortify4Chance|FortifyAddChance|FortifyTierAdjust|MaxPoisons|Poison1Chance|Poison2Chance|Poison3Chance|Poison4Chance|PoisonAddChance|PoisonsTierAdjust|FoodChance|AssocObjects|PotionProperties|FortifyProperties|PoisonProperties|FoodProperties|AllowMixed|StyleScaling

Example:
2|1|VampiresRoyal|210|7|60;70;80;90;100|40;50;60;70;100|10;20;30;40;100|0;5;10;25;40|0;0;8;15;30|0|3|30;35;40;50;60|0;0;10;15;20|0;0;0;5;10|0;0;0;0;0|0;0;0;0;0|0|5|50;60;70;80;100|0;20;30;40;50|0;0;10;20;30|0;0;5;10;20|0;0;0;0;10|0|0;0;0;0;0||<2000007><1,0><800000000,2>|<7fe670cffe3ff8>|<720387dffbffff>|<0>|1|1

The detailed description of the fields is quite long and available here Rule Fields.
If multiple distribution rules with the same name are defined, attachments will always go to the one loaded first.
You can find examples in the distribution file NPCsUsePotions_Default_NUP_DIST.ini

This rule allows to define custom items that may be distributed to actors. There are 5 kinds of items.
"potion" - a potion that is added to list of distributable potions for an actor and may be chosen during distribution.
This can be used to add special potions to the distribution pool of npcs, without having to modify the distribution rule itself.
"poison" - similar to "potion", just for poisons
"fortify" - similar to "potion", just for fortify potions
"food" - similar to "potion", just for food items
"death" - a normal item that will be given to an actor when they die-
"item" - a normal item that will be given to the actor during item distribution, you can choose to give it only once or re-give it when the item was removed from the actor.

1|8|CUSTOMRULEIDENTIFIER|AssocObjects|AssocObjectsChance
Example: 1|8|NUP_Custom_Fletcher|<51592,><E3A4E,>|<3EB2C,Skyrim.esm,1,0,0,200:0,,fortify,100> 
- Adding a fortify Archery potion to the JobFletcher and JobTrainerFaction, if the strength of the actor is
  Weak.

AssocObjects are the objects that the items may be distributed to, AssocObjectsChance defines the custom objects.
For more information see Rule Fields.
You can find other examples in the distribution file NPCsUsePotions_Default_Attachments_NUP_DIST.ini