If you think of a ream of paper as being 500 sheets, and the size of the sheet being 8 1/2" x 11" - you could stack 2 reams of paper, slightly rolled of course, in the 23.5" beneath the lid of a 6x24" time capsule. That would be 1,000 sheets.
2. Yes, you can place it directly into the ground - but not on its side. We recommend it be placed in vertical position - up & down. These instructions & more come with the time capsule. You get a sealant and 1/2 unit of desiccant with this particular basic version.
3. We offer this basic version or you can choose a bundle which has (in addition to the time capsule) a preservation kit to fit the size and 1,000 cc oxygen absorber, too. You don't have to get the preservation kit, but we've loaded it with things like corrosion intercept bags, buffered paper envelopes, acid free tissue, and other items to keep things separate while they lie inside of the time capsule for a long time. We recommend an oxygen absorber because it removes the oxygen from any air that remains in the time capsule. The answer to this question, then, is 'it depends on you.' Sometimes people want things to remain as mint as possible, while other times it's not so important, or they opt to use their own supplies. Remember, it's most important that you have a good time capsule container - one that is airtight & that does not leak.
4. You can safely bury this time capsule for up to 60 years or so - please read and follow all instructions that come with it. You can't expect to place a time capsule to survive standing in water for 25 years no matter what the material is, however.
5. Some of the preservation questions you've asked are answered in the Preservation Hints pamphlet. With this time capsule, we give you that one plus 100 Ideas for Time Capsule Contents, plus 12 Time Capsule Project Tips. You also get a label that you can fill out with indelible marker (like a Sharpie) and a serial number label too. What ink you use should be as archival as possible. The paper should be acid free and have 25% cotton content. But if you have school letterhead, don't hesitate to use it. Put a local newspaper in your time capsule, but be sure to put it in a sleeve or bag. Please see our kit instructions for other information.