I just tried the free version of PDF XChange Viewer/Editor and it works great, but has some limitations that are spelled out when you try to edit contents. Even if you decide to pay for it, it seems very reasonably priced to me.
Another +1 for PDF XChange viewer. I've been using it for years with great results. Mostly I just use the typewriter function to fill in forms and whatnot, if they aren't the autofill type. I haven't bought the paid version, but haven't needed its features so far.
And if you have a fairly new version of MS Word...works quite well.
You could save as PDF starting with 2010, and with 2013 and 2016..edit an existing PDF.
I actually bought Adobe Acrobat DC last month but just switched to PDF X-Change and I like it much better after only using Adobe products. I've been on the hunt for good and free PDF editing for years and nothing quite lives up to the expectations.
I have a customer that loves Nitro PDF. I think the price is about $150 for a business license. I'm not sure if it's worth mentioning but it's not bad.
The caveat I'll add is that it depends on what you're wanting to actually do - if you want to do things like create fillable PDF forms, I'm not aware of any good free options.
If you're looking for that, PDFill PDF Editor is at least cheap, but it's not very polished. I've done a pretty substantial form in it (new patient demographics and health history) and may be able to answer questions if needed.
Free editor for PDF documents. Complete editing of PDF documents is possible with PDFedit. You can change raw pdf objects (for advanced users) or use many gui functions. Functionality can be easily extended using a scripting language (ECMAScript).
Also, there is Pageplus from Serif Software. It's a great desktop publishing app that can do about everything (including PDF forms), but it is recently discontinued. Eventually Pageplus will be replaced by Affinity Publisher, but Publisher isn't available quite yet. For now, you can still get Pageplus licenses for a discounted $25. (used to cost $100).
Serif has made great products for very low prices, in the past. I'm predicting Affinity Publisher to be from $50 to $100 (at most), when it's released.
I loath anything with Adobe and .pdf in the same sentence. I set Chrome to read and display .pdf files and use LibreOffice if I need to edit or create them.