I want to get a trusted file cleaning tool to remove unwanted files.
When I try to add the Ubuntu Tweak repository it says it is from an untrusted repository.
So, are there any trusted file cleaning tools available for Ubuntu?
Software Recommendation – Trusted File Cleaning Tools for Ubuntu
cleanupsoftware-recommendation
Related Solutions
Lightweight
evince - the default document viewer on Gnome/Ubuntu, with support for PDF, PostScript, and a few other formats. Can fill forms, highlight text, and annotate. Normal text selection. Remembers window size and document zoom. Dark mode. [install]
qpdfview(see answer) - tabbed interface, can fill forms, remembers window size and document zoom. Block selection by holding Shift. [install]MuPDF - extremely fast and minimalistic. Block selection by dragging with the right mouse button, search with /. Can't annotate, fill forms, sign, or anything else. Doesn't remember the zoom factor, or the window size/position. [install]
Zathura - extremely fast and minimalistic (uses the MuPDF ending via a plugin system). Keyboard-navigation, bookmarks, auto-reload on changes. Block selection by dragging with the left mouse button. No form filling or other features. Doesn't remember the zoom factor, or the window size/position. [install]
xpdf - "Xpdf is a small and efficient program which uses standard X fonts". Lightweight, but with outdated interface. [install]
gv - an old lightweight pdf viewer with an old interface. Size of the package is only 580k. gv is an X front-end for the Ghostscript PostScript(TM) interpreter. [install]
Full-featured
okular - Multi-format document viewer (PDF, CHM, ePub, others). Requires many KDE prerequisites. Can easily copy text and images. May be slow and have issues with printing. [install]
Browsers like Firefox and Chromium derivatives also have great support for PDF viewing and form filling, but no support for annotations or signatures.
Non-FOSS
Foxit Reader - View, create, convert, annotate, print, collaborate, share, fill forms and sign.
PDF Studio Viewer - free version can annotate, fill&save forms. Paid versions can sign, OCR, split/merge/insert/remove/rotate pages, add watermarks/header/footer/bookmarks, edit, redact, compare, optimize, batch process etc.
Master PDF Editor - View, create, modify, fill forms, sign, scan, OCR, annotate, split/insert/remove/rotate pages, add bookmarks. Free version allows editing text and objects, annotating, and filling forms.
Unsupported/outdated
I'm surprised no one mentioned this:
gnome-subtitles 
It has impressive features, it's extremely easy to use and very well-polished. A lot of care and detail in its UI (check the char count in each line).
I use it all the time to shift subtitle timings to/from HDTV to BDRip/DVDRip releases.
Side-note: VLC player has on-the-fly subtitle timing shift. It will not change your .srt file, only the playback, but it's very convenient for movies you'll only watch once and don't care about saving the adjustments. I assign them to UP and DOWN directional keys.
Best Answer
These are some that could be what you need...
FSLint: Utility collection to find and fix common errors in file storage. It can find things like:
To install, open a terminal Ctrl + Alt + T and enter command:
BleachBit: BleachBit deletes unnecessary files to free valuable disk space, maintain privacy, and remove junk. It removes cache, Internet history, temporary files, cookies, and broken shortcuts.
It handles cleaning of Adobe Reader, Bash, Beagle, Epiphany, Firefox, Flash, GIMP, Google Earth, Java, KDE, OpenOffice.org, Opera, RealPlayer, rpmbuild, Second Life Viewer, VIM, XChat, and more.
Beyond simply erasing junk files, BleachBit wipes free disk space (to hide previously deleted files for privacy and to improve compression of images), vacuums Firefox databases (to improve performance without deleting data), and securely shreds arbitrary files.
To install, open a terminal Ctrl + Alt + T and enter command:
GtkOrphan: A graphical tool to find and remove orphaned libraries. It scans your Debian system, looking for orphaned libraries and helps remove them to claim back your disk space.
To install, open a terminal Ctrl + Alt + T and enter command:
fdupes: Identifies duplicate files within given directories. (FSLint too gives this option to delete duplicate files from the system.)
P.S. The above recommended applications (except fdupes) are in Universe section of Ubuntu's repository. So before starting to install these, you'll have to Enable the “Universe” repository, then update the repos with
sudo apt-get updateand then you can install programs in Universe repo usingapt-get.