In the NLT, it's quite straightforward:
Acts 20:26 (NLT)
26 I declare today that I have been faithful. If anyone suffers eternal death, it’s not my fault,
I was actually amused by the "it's not my fault" part; reminds me of a child. :P
Anyway, other more-literal translations give variations of the following:
Acts 20:26 (NIV)
26 Therefore, I declare to you today that I am innocent of the blood of any of you.
Okay, we can see where the "it's not my fault" part comes from; "innocent".
With more context, the meaning becomes clearer.
Acts 20:25-27 (NIV)
25 “Now I know that none of you among whom I have gone about preaching the kingdom will ever see me again. 26 Therefore, I declare to you today that I am innocent of the blood of any of you. 27 For I have not hesitated to proclaim to you the whole will of God.
Jews would have recognized the reference to (at least) Ezekiel:
Ezekiel 33:8 (NIV)
8 When I say to the wicked, ‘You wicked person, you will surely die,’ and you do not speak out to dissuade them from their ways, that wicked person will die for their sin, and I will hold you accountable for their blood.
Thus, Paul was saying that because he had been preaching God's word to everyone, he couldn't be held accountable for failing to warn someone about their sins and its consequences.