Typed, Targeted Feedback on Student Papers: How To Do It

As a grizzled veteran of the MathTwitterBlogosphere of, let's see, about 5 weeks, I've already seen several really inspiring conversations among teachers (including @davidwees, @k8nowak, @occam98, @cheesemonkeysf, @fawnpnguyen, @absvalteaching, and @TRegPhysics) who are searching for a good way to achieve all of these things at once:

• provide high-quality written feedback on student papers (especially, feedback separate from or instead of scores and grades, since research shows students will only read the grades if both are there)
• avoid repeatedly handwriting the same comments
• have the comments personalized and right beside the work being commented upon
• provide each student (and family?) with an online, commented document instead of or in addition to a physical paper
• do all this without installing expensive software (sometimes, without third-party software at all)
• do all this in a reasonable amount of time and without losing one's sanity

So, here's the best procedure I've come up with so far. If anyone wants to comment and suggest improvements, I'll fold your ideas in, crediting you. 

1. Make a test that has room reserved for your comments: a column to the right or left of the problems, a box under each problem or at the bottom of the page, whatever. Make sure to instruct students not to write in that area. (idea from Trevor Register, whose blog post was passed on by John Burk) 
2. After students take the test, arrange their papers in your class list order (presumably alphabetical). You may want to include blank pages for absent students. Scan the tests into a pdf file. (I'm assuming most of us have access to photocopiers that can do this quickly, but sometimes teachers don't realize it can be done. Ask around if you're not sure!)
3. If you have a Mac, open the pdf file using Preview. (If you have a PC, you'll need some other procedure for steps 3 & 4; I'll add it if someone suggests one.) Add your comments using the Tools/Annotate/Text option: click and drag to make a box to type your text in, and type it in. You can change the color, font, and size for the text box; sadly, you can't do equations. 
4. For your next comment, you don't need to select Tools/Annotate/Text again, just make a new box. If you want to reuse a comment, click on it and copy it, then just paste it in on the next student's paper. When you've finished commenting, save the pdf.
   Here's an example I made using real test questions (leaving out the hardest) and real student work (copied over in my handwriting for privacy reasons). See especially how the comment for #5 is almost identical on the two papers -- no copying by hand, though!!
5. Now you can split the pdf with everyone's papers into individual papers. You can use the free website splitpdf.com for this (found by John Burk). Select the file you are splitting, and use the page range thing (if needed; you'll also use "More+") and "Customize split files' names" to (for example) save student JW's test to jw.pdf. (Entering individual file names is a bit painful; anyone have improvements to suggest?) (splitpdf.com also offers a free Chrome "app," but as far as I can tell that just takes you to their web page. John also found PDFsam, which might be even more powerful but needs to be installed and uses Java.)
6. When you hit "Split!", it will make a .zip file and ask you where on your computer to put it. When you unzip the file, it will make a directory with the student papers stored in it. If you want to, you can then upload the whole directory at once to Google Drive, as I did for my split, commented sample test. 
7. The biggest problem I see is, now how do I share the papers out with the students? Presumably each student could have a directory that they have permissions for and others don't, but shoving each file into the appropriate directory would be a pain. Any thoughts, especially from anyone who's been working with Google Classroom?

Conclusion so far: I would rather do this procedure than write comments on tests by hand. I'd especially like to use it to give students a chance to work more on their papers BEFORE getting the scores/grades. (I would still give highest points to students who did high-quality work in the first round, but I'd give generous partial credit for changes made after my comments.) However, I would like a better way to customize the file names in step 5 and (especially) to painlessly redistribute the commented student papers into appropriate directories where they could access them (step 7).

PS Can you guys actually see the sample files mentioned in Steps 4 & 6? The permissions on the directory, and therefore the files, are supposed to be set so you can, but I'm not sure it's working.