All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
He, sallallaahu ‘alayhi wa sallam, also said: “Whoever (intentionally) ascribes to me what I have not said, then (surely) let him occupy his seat in the Hellfire.” As-Sakhaawi wrote, “Suffice this statement as a severe warning to those who narrate a Hadeeth while knowing that it is false.”
Al-Khateeb Al-Baghdaadi said: “The reporter who narrates Hadeeth should beware of narrating fabricated reports and false Ahaadeeth; whoever intentionally does this bears a manifest sin and is considered among the liars.”
As for the book Hisn Al-Muslim, it is one of the best Hadeeth collections. Its author was keen to verify it, and we have not observed any fabricated Ahaadeeth in it. The author of Hisn Al-Muslim cited the Hadeeth referred to in the question with the following wording: The Prophet, sallallaahu ‘alayhi wa sallam, said: “If anyone says seven times morning and evening: Allaah suffices me: there is no god but He; on Him is my trust - He, the Lord of the Throne (of glory) Supreme, Allaah will be sufficient for him against anything which grieves him from the matters of this worldly life and the Hereafter.” [narrated by Ibn As-Sunni and classified as Saheeh (sound) by Al-Arnaa’oot]
As for the version you mentioned in the question and attributed it to Abu Daawood it had an additional phrase, ‘… whether he is true or false in (repeating) them,’ and this is the reason for classifying the Hadeeth as weak and fabricated. This phrase was not mentioned in the version of the Hadeeth cited in Hisn Al-Muslim.
Hence, you are advised to distribute the pamphlets with the version of the Hadeeth reported by Ibn As-Sunni and not that of Abu Daawood given the inauthenticity of the additional phrase: ‘… whether he is true or false in (repeating) them.’
Allaah Knows best.