Statement: (S)ome happenings in the wake of freedom left a large legacy of misunderstanding.
Your employer(s) were not able to produce substantial documents to support your case. [background: two employer documents were required, a response from someone uses employer(s) - what is this kind of writing?
These two cases are unrelated.
As @RuchirShah correctly observes, the (s) at the end of employer(s) is number-agnostic: you might have one employer or several.
However, the parenthesised (S) at the start of (S)ome has nothing to do with plural or singular. It means the author has altered the quote, either changing capitalisation or inserting an s that was omitted either in the speech or its transcription. In either case, [square brackets] are usually preferred, and many style guides may not require you to indicate the former.
[Edited to clarify varying style practices]
In case 2, “employer(s)” is an abbreviation for “employer or employers.” You will sometimes also see “employer/s,” or “(s)he.”
Case 1 is not standard written English. What probably happened is that the author is quoting from the middle of a sentence like, “I saw that some events in the wake of freedom ....” In the new context, “some” becomes the first word of a sentence, so it should be capitalized. This alters the original text, so it should be written, “[S]ome.” (Note that, in American English, changing the final punctuation as I just did is an exception to that rule, but British English would have required me to add the period outside the quotation marks.)
Your source seems to have substituted parentheses for brackets. The most likely reason is that they are using a keyboard with no square brackets, such as a German keyboard. (Especially since the style suggests an academic writing in English as a second language.) They might also have been using a content-management system where
[S] is valid markup, such as BBcode.
(s) is known as the plural in brackets. Use mostly in the case when the singular and the plural form can be used. employer(s) here stands for one or more (for singular and plural), so in both case, if it can be used.