しおり機能の非表示にしたい

@ka_4060 yes, this can be done. BUT, this requires a full version of Adobe Acrobat (Standard or Pro), as Adobe Acrobat Reader cannot save these changes. You could prevent the bookmarks (and other) navigation panes from opening if you manually close them once. Go to the Preferences, and under the Open Settings section, check the box for "Restore last view settings when reopening documents" (the exact wording may vary slightly, such as "Remember current state of Tools Pane" or "Remember last state of All tools pane when opening documents").