Think about the conditions under which your guidebook is actually read.
One-handed, because the other hand has a suitcase in it. On a phone, outdoors, in sunlight, or in bed with the lights off. By someone who has been travelling for nine hours. Possibly in their second or third language. Often with a low battery, which on many phones means a dimmed screen and no background loading.
Almost no other document you write has to survive that. It changes what good writing looks like.
Structure
Put the thing they need first. The order of your sections is not a table of contents, it is a probability ranking. WiFi, check-in, and check-out get opened ten times more than the section about the building's history. Order accordingly, and put nothing above them.
One idea per section. A section called "Arrival and parking and house rules" is three sections wearing a coat. Guests navigate by heading, and a heading that covers three topics cannot be scanned.
Headings that name things, not themes. "Parking" beats "Getting around". "Bin day" beats "Sustainability". A guest scanning for an answer is matching a word in their head against words on a screen, and the word in their head is a noun.
Front-load every paragraph. The answer in the first sentence, the detail after. A guest who stops reading after one line should still have what they came for.
Typography and contrast
16px minimum, and larger for anything transactional. A WiFi password or a door code should be set noticeably bigger than body text. It is the string most likely to be read in bad light and most likely to be mistyped.
Contrast that survives sunlight. Light grey text on white looks refined on a designer's monitor and disappears on a phone at half brightness on a beach. The formal target is 4.5:1 for body text; the practical test is to walk outside with your phone and try to read it.
Avoid ambiguous characters in anything to be typed. In many typefaces l, I and 1 are identical, as are 0 and O. Choose passwords and codes that avoid them, or set them in a typeface where they differ.
Line length under about 70 characters. On a phone this happens naturally. It stops happening the moment you paste in a table.
Things to tap
Make the WiFi password copyable with one tap. A fourteen-character password typed by hand in the dark will be typed wrong at least once. A copy button removes the whole failure class.
Phone numbers should dial. Addresses should open in a maps app. If a guest has to select, copy, switch apps and paste, some of them will simply message you instead.
Tap targets of 44 by 44 points or more. A tired person misses small buttons. Two small buttons close together produce a mis-tap, which produces the impression that the thing is broken.
What to cut
Tables. They do not fit. A table with four columns becomes a horizontally scrolling mess on a phone, and horizontal scroll is the single most reliable way to lose a reader. Turn it into a short list.
PDFs as the primary format. A PDF on a phone is a pinch-zoom experience and the text does not reflow. A printable PDF is a good thing to be able to produce — for a binder, or for a guest who wants something on paper — but it is a poor thing to hand someone as their only route to the door code.
Walls of emoji. One or two as section markers is fine. A line of them reads as noise and breaks screen readers, which read each one aloud by name.
Anything written in capitals. ALL CAPS is slower to read for everyone and considerably slower for dyslexic readers, and it reads as shouting, which is rarely the tone you want for a house rule.
The accessibility items that matter here
Real alt text on photographs. "Lockbox" is not alt text. "A black combination lockbox mounted on the right-hand porch wall, below a white mailbox" is, and it is the difference between a blind guest finding the box and not.
Do not rely on colour alone. If the recycling bin is identified only by being blue in a photo, a colour-blind guest has no information. Name it as well.
Let the page zoom. Anything that blocks pinch-zoom locks out every guest who needs larger text.
The first screen
Whatever a guest sees without scrolling is doing most of the work. Mine has four things: the property name, the door code, the WiFi, and my phone number. Everything else is below.
That is an unglamorous first screen. It is also the reason the phone stops ringing.
Two tests
The sunlight test. Take your phone outside on a bright day, set brightness to half, and read your own guidebook. Whatever you cannot read is a contrast failure, regardless of what any tool says.
The one-hand test. Hold the phone in one hand, in the hand you do not write with, and try to get from the top of the guidebook to the WiFi password using only your thumb. If you have to shift your grip, the layout is wrong.
Both take a minute. Both find things a desk review never will.