My first thought on this would be Laserfiche Forms Portal where you could get an electronic signature for everyone who goes to the site and reads the memo. 

If you don't have that you need to determine if everyone has access to Laserfiche (i.e. their own login). If they do you could have them acknowledge it by creating a workflow that sets the security to only that person and then have them change a metadata field to acknowledge it. 

Assuming neither of those are true, I'd build a workflow that took a scanned copy of the memo with a generic cover page on the back.  At this point it would reference a SQL table that has an index field, the person's name, an email address and a field to indicated if they have signed. On that cover page I'd have a place that they could sign and use a text box to place the persons name, and a separate text box in a couple of places that has a unique code that includes the index number. When the user reads that memo, they will email a scan of that page to someone (or scan to a folder monitored by import agent). 

When the person who collects those emails places them in Laserfiche an OCR process should let you pick up the person's name if you have designed the text box correctly. I tend to design a "code" for scanning and place it in 2 different places with something like "HHH (Code) HHH". Some easy to OCR set of letters, the code, and another set of letters. 

Then you can simply set a seperate workflow to extract the text from each of these pages, find the HHH AAA ##### HHH with pattern match and extract the numbers. The numbers would ideally just be the index # of the distribution list DB you created. The AAA pattern of letters would figure out which distribution list it is, so it knows which DB to look at to figure out which name was checked and mark it as signed.

If you want you can have an additional workflow run periodically to look through your db's to see if there are any that are not signed.