I'm trying to make a vinyl rip sound clean as a digital copy in several steps and the first is increasing high frequencies slightly and turning down the overall gain to prevent clipping. Whoever wants to point out that it's easier to buy the digital copy, well they don't sell particular track digitally. The audio looked this way and after applying aforementioned manipulations it actually sounds better but I noticed that it looks somewhat weird i.e. vertically asymmetrical, as if the left channel were dragged downwards and right one upwards, I doubt the master looked that way originally. Please explain what is the issue here and what can I do about it?
Vertical asymmetry's not a problem; likely just a product of the phase relationships between the superimposed sounds. There are ways of rectifying it (google phase rotator plugins) but it's no harm.
It's not DC offset - the entire waveform, including the silence at the beginning/end, would be shifted vertically one way or the other away from the infinity line if that were the case. (DC offset can be removed with a Hi-Pass filter set at 20Hz or somewhere thereabouts).
Sound on sound article with more info here: http://www.soundonsound.com/sos/may13/articles/qanda-0513-1.htm
Might be worth re-ingesting it in any case, though, leaving yourself some more headroom; both waveforms look quite clipped!