Feedback on Schematic Design (Fully Annotated, Following Design Guidelines; with Purpose Statement and Datasheets)
Well, a few things.

Readability


Draw landscape mode on a standard size. 17x11 is good (or its closest metric equivalent), is about the right size for viewability on screen and in printing, yet gives enough room for stuff.
Normal place for the title block is the lower right of the page. It should include at least the following:


project name
page title
document number
document revision
date
page number
number of pages

Have a cover page with a block diagram.
Have a Revision History
Hierarchical schematics don't really work for a small design. It doesn't do the documenting job that a block diagram can do. Just draw a flat design.
Put more things on each page, grouping like elements together.
Use off-pages to connect elements. Your drawing tool should support automatically adding page references (annotation.)
Where's the pin numbers and pin names? Need to have those.


Design Information


Add some kind of a mechanical plan (doesn't have to be exact.)
Prepare a PCB stackup plan. Number of layers, copper weight, thickness.
Identify any signals that require special layout (differential pairs, impedance control, power traces, etc.)
All your ICs and active components should have a part type call-out, with some kind of package information (e.g., 'L7805-TO-220').
For specialty components, it's helpful to show a manufacturer part number as a reference (such as the rotary encoder, relay, others).
All your parts should have a footprint (sometimes called a 'decal') assigned. You may decide to display this on the schematic, or not. You will need it for layout, and the footprint call-out has to be in the PCB layout library, or it needs to be created as a new part.
For passive components, include any critical information.


Resistors: value, tolerance, power rating if other than minimal
Capacitors: value, tolerance, voltage rating, formulation
Inductors: value, tolerance, specific part number (standardization is poor for these.)



Manufacturing Information


Understand thoroughly how your CAD tool creates a Bill of Material (BOM).


Especially, learn how to merge in external part data when you create your BOM.
Make up an internal part numbering system for all your parts. It doesn't matter what numbering system you use, so long as each part type is unique.
For each part type that you create, include a detailed description, and a list of exact manufacturer part numbers (your Approved Vendor List, or AVL.) Organizing this in a master spreadsheet works well.
Add this part number as an attribute to each part on your schematic.

Displaying your assigned part number on the schematic is optional. I don't do it now, but have worked at places that required it.


I’ll add (still) more in due time.