PDA decls are probably the easiest decl to understand because they are so simple. There is an editor for PDAs (editPDAs) not because they are hard, but because they are tedious (especially when you are making 100 of them).

A PDA is actually made up of multiple decls. There is the PDA itself, then there are the emails that go in the PDA, the Audio Logs, and the Videos. Note in vanilla Doom 3, the 'Personal' PDA is the only PDA that can contain videos, but it cannot contain any Audio Logs. If there is a video in a non-personal PDA, it gets copied to the Personal PDA when it is picked up. Doom 3 actually defines 'Personal PDA' to mean whichever PDA is picked up first, so it's up to the level designer to make sure the actual personal PDA is picked up before any others.

Let's take a look at the PDA for James Holiday:

pda commoutside_holiday {
    name         "James Holiday"
    fullname     "James A. Holiday"
    icon         "guis/assets/pda/icon_jholiday"
    id           "7085-64"
    post         "Communications Transfer"
    title        "Transport Controller"
    security     "COMM Transfer Access"
    pda_email    "commoutside_holiday_email_1"
    pda_email    "commoutside_holiday_email_2"
    pda_audio    "commoutside_holiday_audio_1"
}

Pretty simple to figure out I hope. The icon is not actually used in Doom 3, but we were going to use it at one time. Everything in there is for display purpose only, which means if you change the 'security' key, it doesn't actually change your security clearance (it only changes what it says your security clearance is). Actual security clearance is defined by the presence or abscense of various items in your inventory.

let's take a look at an email:

email commoutside_holiday_email_2 {
    date    "11-15-2145"
    to      "James Holiday"
    from    "Shipping Authority"
    subject "Site 1 needs"
    text {
        "Blah blah, this is an email.\n\n"
        "Blah blah, this is line 2\n\n"
        "-Shipping Authority"
    }
}

The format for the email is pretty self explanitory. The biggest 'gotcha' (and the biggest reason to use the editor) is every line has to be in quotes, and you have to use \n to create new lines. That has been the biggest reason for PDAs to break during Doom 3 development.

Now let's look at the audio log:

audio commoutside_holiday_audio_1 {
    name    "Artifact Transport Concerns"
    info    "Made by: James Holiday\nDate: 09-24-2145\nArchive: Yes"
    preview "sound/vo/video/novideo"
    audio   "audiolog_commoutside_holiday_1"
}

Again, pretty self explanitory. The info and preview didn't end up getting used in the final build of the game, but at one time the gui showed little icons and info beside each audio log. Now all you really need is 'name' and 'audio'

Next, let's take a look at the first video you get when you pick up your PDA:

video marine_sop {
    name    "Marine Command Briefing"
    info    "Creator: Marine HQ\nDate: 03/11/45\n\nOperating Procedures\n"
    video   "video/video_marine_sops"
    audio   "video_marine_sops"
    preview "guis/assets/cpuserver/uac.tga"
}

Again, info is just used for display. Preview is the image shown in the box before you hit 'play'. Video is the material to use after you hit play (technically it can be any material, but a material with a roq in it makes the most sense). Audio is the sound to play in sync with the video.

Videos can be attached to video discs by setting the 'video' key on an 'item_videocd' entity.