### #1

[Trott-Strzebonski in-place evaluation][1]:

    hf = HoldForm[1 - 1^2/2 + 1^3/3 - 1^4/4 + 1^5/5 - 1^6/6]

    hf /. x_Times :> With[{eval = x}, eval /; True]

>     1 - 1/2 + 1/3 - 1/4 + 1/5 - 1/6

    Replace[hf, x_ :> With[{eval = x}, eval /; True], {2}]

>     1 - 1/2 + 1/3 - 1/4 + 1/5 - 1/6

One may simplify this method using the undocumented function `RuleCondition` as [WReach shows][3]:

    Replace[hf, x_ :> RuleCondition[x], {2}]

>     1 - 1/2 + 1/3 - 1/4 + 1/5 - 1/6

### #2

[Injector pattern][2]:

    {1, -(1/2), 1/3, -(1/4), 1/5, -(1/6)} /. {x__} :> HoldForm[+x]

>     1 - 1/2 + 1/3 - 1/4 + 1/5 - 1/6




  [1]: http://library.wolfram.com/conferences/devconf99/villegas/UnevaluatedExpressions/Links/index_lnk_30.html
  [2]: http://mathematica.stackexchange.com/a/1937/121
  [3]: http://mathematica.stackexchange.com/a/2683/121