This section is from the book "Hill's Manual Of Social And Business Forms: A Guide To Correct Writing", by Thos. E. Hill. Also available from Amazon: Hill's Manual Of Social And Business Forms: The How-To-Do-Everything Book Of Victorian America.
Pledge - pawn, deposit, security, hostage, earnest.
Plentiful - bounteous, abundant, copious, exuberant, ample, plenteous.
Pliant - lithe, limber, yielding, bending, supple, flexible, pliable.
Plight - predicament, state, case, situation, condition, conjuncture.
Plot - plan, arrangement, project, conspiracy, combination, scheme, intrigue.
Polite - courteous, well-bred, civil, polished, refined, genteel, affable.
Politeness - good manners, civility, courtesy, suavity, good breeding.
Politic - wise, careful, artful, cunning, civil, prudent.
Pollute - corrupt, taint, defile, infect, contaminate.
Pompous - lofty, stately, ostentatious. showy, dignified, magnificent.
Ponder - study, reflect, think, muse, consider.
Portion - piece, part, quantity, share, division, dower, fortune.
Positive - confident, certain, real, dogmatic, sure, absolute.
Possess - keep, hold, have, enjoy, occupy.
Postpone - retard, delay, prolong, protract, defer, procrastinate.
Potent - -powerful, strong, vigorous, mighty, forcible.
Poverty - want, need, indigence, penury, suffering.
Practicable - possible, feasible, available.
Practice - custom, style, manner, form, use, habit.
Praise - eulogize, applaud, laud, admire, commend.
Precarious - uncertain, dubious, doubtful, equivocal, unreliable.
Precedence - priority, superiority, preference.
Preceding - anterior, previous, prior, antecedent, former, foregoing.
Precious - choice, costly, valuable, expensive, uncommon, rare.
Precise - careful, particular, exact, accurate, correct, nice.
Preclude - intercept, prevent, obviate, hinder.
Predicament - condition, plight, position, situation.
Predict - prophesy, foretell.
Predominant - prevalent, overruling, controlling, supreme, prevailing.
Predominate - prevail, rule over.
Preference - advancement, priority, choice.
Prejudice - bias, injury, hurt, disadvantage.
Preliminary - previous, preparatory, introductory, antecedent.
Prepare - arrange, qualify, fit, equip, make ready.
Preposterous - impossible, ridiculous, absurd, foolish.
Prerogative - immunity, privilege.
Prescribe - dictate, ordain, appoint.
Preserve - uphold, maintain, pro-tect, spare, save.
Pressing - urgent, emergent, importunate, crowding, squeezing, forcing.
Presume - guess, suppose, think, surmise, conjecture, believe.
Presuming - forward, arrogant, presumptuous.
Pretext - excuse, pretense, pretension.
Pretty - lovely, beautiful, fine, agreeable.
Prevailing - dominant, ruling, overcoming, prevalent, predominating.
Prevent - impede, obstruct, hinder, obviate, preclude.
Previous - before, prior, anterior, preliminary, introductory.
Price - value, worth, expense, cost.
Pride - self-esteem, arrogance, haughtiness, conceit, ostentation, loftiness, vanity.
Primary - elemental, first, original, pristine.
Principal - main, chief, capital, head, leading, important.
Principle - motive, tenet, constituent part, doctrine, element.
Print - impress, stamp, mark. Prior - before, previous, former, antecedent, preceding, anterior.
Priority - preference, precedence, pre-eminence.
Pristine - original, first, primitive.
Privacy - seclusion, solitude, retirement, loneliness.
Privilege - prerogative, right, advantage, immunity, exemption.
Probability - supposition, likelihood, chance.
Probity - reliability, uprightness, honesty, integrity, veracity.
Proceed - progress, arise, issue, advance, emanate.
Proceeding - transaction, course, progression, work.
Proclaim - declare, publish, announce, tell, advertise, promulgate.
Proclivity - liking, tendency, inclination, proneness.
Procure - obtain, acquire, gain.
Prodigal - lavish, extravagant, wasteful.
Prodigious - great, astonishing, vast, large, amazing, monstrous.
Profane - secular, irreverent, impious, irreligious.
Profession - calling, employment, business, vocation, work, labor.
Proficiency - advancement, improvement, progress.
Profit - gain, advantage, benefit, emolument.
Profligate - depraved, wicked, corrupt, sinful, vicious, abandoned.
Profuse - lavish, wasteful, prodigal, extravagant.
Progeny - descendants, offspring, race, issue.
Project - invent, design, scheme, plan.
Prolific - productive, fruitful, fertile.
Prolix - tiresome. long, diffuse.
Prolong - extend, delay, protract, postpone, retard, procrastinate.
Prominent - eminent, conspicuous, distinguished.
Promise - agreement, assurance, engagement, declaration, pledge, word, obligation.
Promote - raise, encourage, forward, advance.
Prompt - quick, active, ready, assiduous.
Pronounce - say, speak, utter, declare, affirm, articulate, enunciate.
Proof - evidence, testimony, argument.
Propagate - multiply, increase, disseminate, diffuse, circulate, spread, extend.
Propensity - liking, inclination, proneness, tendency, bias.
Proper - fit, right, suitable, just, appropriate.
Propitious - favorable, auspicious.
Propitiate - conciliate, appease, reconcile.
Proportionate - equal, adequate, commensurate.
Propose - offer, apply, tender, intend, purpose, bid.
Prospect - view, landscape, survey.
Prospective - future, foreseeing, hereafter, forward.
Prosperous - fortunate, lucky, flourishing, successful.
Protect - uphold, guard, shield, maintain, defend, cherish, foster, patronize.
Protract - withhold, retard, prolong, delay, defer, postpone.